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Perhaps I wrapped up my exploration of disk system performance one day too early. (While it is Friday here in Malaysia, it is still only Thursday back home)
Barry Burke, EMC blogger (aka The Storage Anarchist) writes:
Aren't you mixing metrics here?
This is a fair question, Barry, so I will try to address it here.
It was not a typo, I did mean MPG (miles per gallon) and not MPH (miles per hour). It is always challenging to find an analogy that everyone can relate to explain concepts in Information Technology that might be harder to grasp. I chose MPG because it was closely related to IOPS and MB/s in four ways:
It seemed that if I was going to explain why standardized benchmarks were relevant, I should find an analogy that has similar features to compare to. I thought about MPH, since it is based on time units like IOPS and MB/s, butdecided against it based on an earlier comment you made, Barry, about NASCAR:
Let's imagine that a Dodge Charger wins the overwhelming majority of NASCAR races. Would that prove that a stock Charger is the best car for driving to work, or for a cross-country trip?
Your comparison, Barry, to car-racing brings up three reasons why I felt MPH is a bad metric to use for an analogy:
You also mention, Barry, the term "efficiency" but mileage is about "fuel economy".Wikipedia is quick to point out that the fuel efficiency of petroleum engines has improved markedly in recent decades, this does not necessarily translate into fuel economy of cars. The same can be said about the performance of internal bandwidth ofthe backplane between controllers and faster HDD does not necessarily translate to external performance of the disk system as a whole. You correctly point this out in your blog about the DMX-4:
Complementing the 4Gb FC and FICON front-end support added to the DMX-3 at the end of 2006, the new 4Gb back-end allows the DMX-4 to support the latest in 4Gb FC disk drives.
This also explains why the IBM DS8000, with its clever "Adaptive Replacement Cache" algorithm, has such highSPC-1 benchmarks despite the fact that it still uses 2Gbps drives inside. Given that it doesn't matter between2Gbps and 4Gbps on the back-end, why would it matter which vendor came first, second or third, and why call it a "distant 3rd" for IBM? How soon would IBM need to announce similar back-end support for it to be a "close 3rd" in your mind?
I'll wrap up with you're excellent comment that Watts per GB is a typical "green" metric. I strongly support the whole"green initiative" and I used "Watts per GB" last month to explain about how tape is less energy-consumptive than paper.I see on your blog you have used it yourself here:
The DMX-3 requires less Watts/GB in an apples-to-apples comparison of capacity and ports against both the USP and the DS8000, using the same exact disk drives
It is not clear if "requires less" means "slightly less" or "substantially less" in this context, and have no facts from my own folks within IBM to confirm or deny it. Given that tape is orders of magnitude less energy-consumptive than anything EMC manufacturers today, the point is probably moot.
I find it refreshing, nonetheless, to have agreed-upon "energy consumption" metrics to make such apples-to-apples comparisons between products from different storage vendors. This is exactly what customers want to do with performance as well, without necessarily having to run their own benchmarks or work with specific storage vendors. Of course, Watts/GB consumption varies by workload, so to make such comparisons truly apples-to-apples, you would need to run the same workload against both systems. Why not use the SPC-1 or SPC-2 benchmarks to measure the Watts/GB consumption? That way, EMC can publish the DMX performance numbers at the same time as the energy consumption numbers, and then HDS can follow suit for its USP-V.
I'm on my way back to the USA soon, but wanted to post this now so I can relax on the plane.
technorati tags: IBM, EMC, Storage Anarchist, MPG, MPH, IOPS, NASCAR, Malaysia, Watts, GB, green, back-end, DMX-3, DMX-4, HDS, USP, USP-V, SPC, SPC-1, SPC-2, standardized, benchmarks, workload, DS8000, disk, storage, tape[Read More]
This week and next I am touring Asia, meeting with IBM Business Partners and sales repsabout our July 10 announcements.
Clark Hodge might want to figure out where I am, given the nuclearreactor shutdowns from an earthquake in Japan. His theory is that you can follow my whereabouts just by following the news of major power outages throughout the world.
So I thought this would be a good week to cover the topic of Business Continuity, which includes disaster recovery planning. When making Business Continuity plans, I find it best to work backwards. Think of the scenarios that wouldrequire such recovery actions to take place, then figure out what you need to have at hand to perform the recovery, and then work out the tasks and processes to make sure those things are created and available when and where needed.
I will use my IBM Thinkpad T60 as an example of how this works. Last week, I was among several speakers making presentations to an audience in Denver, and this involved carrying my laptop from the back of the room, up to the front of the room, several times. When I got my new T60 laptop a year ago, it specifically stated NOT to carry the laptop while the disk drive was spinning, to avoid vibrations and gyroscopic effects. It suggested always putting the laptop in standby, hibernate or shutdown mode, prior to transportation, but I haven't gotten yet in the habit of doing this. After enough trips back and forth, I had somehow corrupted my C: drive. It wasn't a complete corruption, I could still use Microsoft PowerPoint to show my slides, but other things failed, sometimes the fatal BSOD and other times less drastically. Perhaps the biggest annoyance was that I lost a few critical DLL files needed for my VPN software to connect to IBM networks, so I was unable to download or access e-mail or files inside IBM's firewall.
Fortunately, I had planned for this scenario, and was able to recover my laptop myself, which is important when you are on the road and your help desk is thousands of miles away. (In theory, I am now thousands of miles closer to our help desk folks in India and China, but perhaps further away from those in Brazil.) Not being able to respond to e-mail for two days was one thing, but no access for two weeks would have been a disaster! The good news: My system was up and running before leaving for the trip I am on now to Asia.
Following my three-step process, here's how this looks:
technorati tags: IBM, July, announcements, earthquake, Japan, nuclear reactor, power, outage, business, continuity, disaster, recovery, plan, plans, planning, IBM, Thinkpad, T60, laptop, Windows, Denver, BSOD, VPN, India, China, Brazil, help desk, Asia, Tivoli, Storage, Manager, TSM, BMR, external, USB, bootable, CD, DVD, separating, programs, data, Clark Hodge[Read More]
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Yesterday, I started this week's topic discussing the various areas of exploration to helpunderstand our recent press release of the IBM System Storage SAN Volume Controller and itsimpressive SPC-1 and SPC-2 benchmark results that ranks it the fastest disk system in the industry.
Some have suggested that since the SVC has a unique design, it should be placed in its own category,and not compared to other disk systems. To address this, I would like to define what IBM meansby "disk system" and how it is comparable to other disk systems.
When I say "disk system", I am going to focus specifically on block-oriented direct-access storage systems, which I will define as:
One or more IT components, connected together, that function as a whole, to serve as a target forread and write requests for specific blocks of data.
Clarification: One could argue, and several do in various comments below, that there are other typesof storage systems that contain disks, some that emulate sequential access tape libraries, some that emulate file-systems through CIFS or NFS protocols, and some that support thestorage of archive objects and other fixed content. At the risk of looking like I may be including or excluding such to fit my purposes, I wanted to avoid appl
People who have been working a long time in the storage industry might be satisfied by this definition, thinkingof all the disk systems that would be included by this definition, and recognize that other types of storage liketape systems that are appropriately excluded.
Others might be scratching their heads, thinking to themselves "Huh?" So, I will provide some background, history, and additional explanation. Let's break up the definition into different phrases, and handle each separately.
So, the SAN Volume Controller is a disk system comprising of one to four node-pairs. Each node is a piece of IT equipment that have processors and cache. These node-pairs are connected to a pair of UPS power supplies to protect the cache memory holding writes that have not yet been de-staged. The combination of node-pairs and UPS acting as a whole, is able to serve as a target to SCSI commands sent over Fibre Channel cables on a Storage Area Network (SAN). To read some blocks of data, it uses its internal cache storage to satisfy the request, and for others, it goes out to external disk systems that contain the data required. All writes are satisfied immediately in cache on the SVC, and later de-staged to external disk when appropriate.
As of end of 2Q07, having reached our four-year anniversary for this product, IBM has sold over 9000 SVC nodes, which are part of more than 3100 SVC disk systems. These things are flying off the shelves, clocking in a 100% YTY growth over the amount we sold twelve months ago. Congratulations go to the SVC development team for their impressive feat of engineering that is starting to catch the attention of many customers and return astounding results!
So, now that I have explained why the SVC is considered a disk system, tomorrow I'll discuss metrics to measure performance.
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Chris Evans over at Storage Architect posts aboutHardware Replacement Lifecycle Update, on how storage virtualization can helpwith storage hardware replacemement. He makes two points that I would like to comment on.
In a typical four year lifecycle of storage arrays, it might take six months or so to fill up the box, and might takeas much as a year at the end to move the data out to other equipment. SVC can greatly reduce both of these, so that you can take immediate advantage of new equipment as soon as possible, and keep using it for close to the full four years,migrating weeks or days before your lease expires.
Seth Godin has an interesting post titled Times a Million.He recounts how many people determine the fuel savings of higher-mileage cars to be only $300-$900 per year,and that this is not enough to motivate the purchase of a more-efficient vehicle, such as a hybrid orelectric car. Of course, if everyone drove more efficient vehicles, the benefits "times a million" wouldbenefit everyone and the world's ecology.
When I discuss storage-related concepts, many executives mistakenly relate them to the one area of information technologythey know best: their laptop. Let's take a look at some exam Information Lifecycle Management (ILM) includes classifying data by business value, and then using this to determineplacement, movement or deletion. If you think about the amount of time and effort to review the files on yourindividual laptop, and to manually select and move or delete data, versus the benefits for the individual laptopowner, you would dismiss the concept. Most administrative tasks are done manually on laptops, because automatedsoftware is either unavailable or too expensive to justify for a single owner. In medium and large size enterprises, automated software to help classify, move and delete data makes a lot of sense.Executives who decide that ILM is not for their data center, based on their experiences with their laptop, are losingout on the "times a million" effect. Laptops have various controls to minimize the use of battery, and these controls are equally available when pluggedin. Many users don't bother turning off the features and functions they don't need when plugged in, because theyfeel the cost savings would only amount to pennies per day. Times a million, energy savings do add up, and options to reduce the amount used per server, per TB of data stored, not only save millions of dollars per year, but can also postpone the need to build a new data center, or upgrade the electrical systems in your existing data center. I am not surprised how many laptops do not have adequate backup and disaster recovery plans. When executives thinkin terms of the time and effort to backup their data, often crudely copying key files to CDrom or USB key, and worryingabout the management of those copies, which copies are the latest, and when those copies can be destroyed, theymight reject deploying appropriate backup policies for others. Times a million, the collected data stored on laptops could easily be half of your companies emails and intellectual property. Products like IBM Tivoli Storage Manager can manage a large number of clients with a few admi So, next time you are looking at technology or solutions for your data center, don't suffer from "Laptop Mentality". Focus instead on the data center as a whole.
Information Lifecycle Management (ILM) includes classifying data by business value, and then using this to determineplacement, movement or deletion. If you think about the amount of time and effort to review the files on yourindividual laptop, and to manually select and move or delete data, versus the benefits for the individual laptopowner, you would dismiss the concept. Most administrative tasks are done manually on laptops, because automatedsoftware is either unavailable or too expensive to justify for a single owner.
In medium and large size enterprises, automated software to help classify, move and delete data makes a lot of sense.Executives who decide that ILM is not for their data center, based on their experiences with their laptop, are losingout on the "times a million" effect.
Laptops have various controls to minimize the use of battery, and these controls are equally available when pluggedin. Many users don't bother turning off the features and functions they don't need when plugged in, because theyfeel the cost savings would only amount to pennies per day.
Times a million, energy savings do add up, and options to reduce the amount used per server, per TB of data stored, not only save millions of dollars per year, but can also postpone the need to build a new data center, or upgrade the electrical systems in your existing data center.
I am not surprised how many laptops do not have adequate backup and disaster recovery plans. When executives thinkin terms of the time and effort to backup their data, often crudely copying key files to CDrom or USB key, and worryingabout the management of those copies, which copies are the latest, and when those copies can be destroyed, theymight reject deploying appropriate backup policies for others.
Times a million, the collected data stored on laptops could easily be half of your companies emails and intellectual property. Products like IBM Tivoli Storage Manager can manage a large number of clients with a few admi
So, next time you are looking at technology or solutions for your data center, don't suffer from "Laptop Mentality". Focus instead on the data center as a whole.
Continuing my business trip through Asia, I have left Chengdu, China, and am now in Kuala Lumpur, Malaysia.
On Sunday, a colleague and I went to the famous Petronas Twin Towers, which a few years ago were officially the tallestbuildings in the world. If you get there early enough in the day, and wait in line for a few hours, you can get a ticket permitting you to go up to the "Skybridge" on the 41st floor that connects the two buildings. The views are stunning, and I am glad to have done this.(If you are afraid of heights, get cured by facing your fears with skydiving)
You would think that a question as simple as "Which is the tallest building in the world?" could easily be answered, given that buildings remain fixed in one place and do not drastically shrink or get taller over time or weather conditions, and the unit of height, the "meter", is an officially accepted standard in all countries, defined as the distance traveled by light in absolute vacuum in 1/299,792,458 of a second.
The controversy stems around two key areas of dispute:
To bring some sanity to these comparisons, the Council on Tall Buildings and Urban Habitat has tried to standardize the terms and definitions to makecomparisons between buildings fair. Why does all this matter whose building is tallest? It matters in twoways:
What does any of this have to do with storage? Two weeks ago, IBM and the Storage Performance Councilanswered the question "Which is the fastest disk system?" with apress release. Customers thatcare about performance of their most mission critical applications are often willing to pay a premium to run theirapplications on the fastest disk system, and the IBM System Storage SAN Volume Controller, built through aglobal collaboration of architects and engineers across several countries, is (in my opinion at least) an impressive feat of storage engineering.
EMC bloggerChuck Hollis was the first to question the relevance of these results, and I failed to "turn the other cheek" and responded accordingly. The blogosphere erupted, with more opinions piled on by others, many from EMC andIBM, found in comments on these posts or other blogs, some have since been retracted or deleted, while othersremain for historical purposes.
At the heart of all this opinionated debate, lies a few areas of exploration:
I will try to address some of these issues in a series of posts this week.
technorati tags: IBM, KL, Kuala Lumpur, Malaysia, Petronas, Twin Towers, SkyBridge, tallest, building, structure, tower, fasted, disk, system, SVC, SAN Volume Controller, EMC, Chuck Hollis, SPC, Storage Performance Council
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Avi Bar-Zeeb of RealityPrime has an interesting post aboutHow Google Earth [really] Works.Normally, people who are very knowledgeable in a topic have a hard time describing concepts in basic terms. Avi was one of the co-founders of Keyhole, the company that built the predecessor for Google Earth, and also worked with Linden Lab for its 3D rendering it its virtual world, so he certainly knows what he is talking about. While he sometimes drops down into techno-talk about patents, the post overall is a good read.
It is perhaps human nature to be curious on how things are put together and how they function, leading to the popularity of web sites like www.
Many things can be used without understanding their internal inner workings. You can put on a pair of blue jeans without knowing how the cotton was made into denim fabric; lace up your favorite pair of running shoes without understanding the chemical make-up of the plastic that cushions your feet; or drink a glass of beer after your five mile run without knowing how alcohol is processed by your liver.
For technology, however, some people insist they need to know how it works in order for them to get the most use of it. When shopping for a car, for example, a guy might look under the hood, and ask questions about how the engine works, while his wife sits inside the vehicle, counting cup holders and making sure the radio has all the right buttons.
Not all technology suffers from need-to-know-itis. For example, the Apple iPod music player and the Canon PowerShot digital camera, are both just disk systems that read and write data, with knobs and dials on one end, and ports for connectivity on the other. Everyone just asks how to use their controls, and might read the manual to understand how to connect the cables. Few people who use these devices ask how they work before they buy them.
Other disk systems, the kind designed for data centers for the medium and large enterprise, apparently aren't there yet. Storage admins who might happily own both an iPod player and a PowerShot camera, insist they need to know how the technologies inside various storage offerings work. Is this just curiosity talking? Or are there some tasks like configuration, tuning, and support that just can't be done without this knowledge? Does knowing the inner workings somehow make the job more enjoyable, easier, or performed with less stress?
I'm curious what you think, send me a comment on this.
technorati tags: Avi Bar-Zeeb, Google, Earth, cotton, demin, plastic, shoes, beer, alcohol, liver, IBM, disk, system, storage, technology, Apple, iPod, music, player, Canon, PowerShot, digital, camera[Read More]
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Wrapping up this week's exploration on disk system performance, today I willcover the Storage Performance Council (SPC) benchmarks, and why I feel they are relevant to help customers make purchase decisions. This all started to address a comment from EMC blogger Chuck Hollis, who expressed his disappointment in IBM as follows:
You've made representations that SPC testing is somehow relevant to customers' environments, but offered nothing more than platitudes in support of that statement.
Apparently, while everyone else in the blogosphere merely states their opinions and moves on,IBM is held to a higher standard. Fair enough, we're used to that.Let's recap what we covered so far this week:
Today, I will explore ways to apply these metrics to measure and compare storageperformance.
Let's take, for example, an IBM System Storage DS8000 disk system. This has a controller thatsupports various RAID configurations, cache memory, and HDD inside one or more frames.Engineers who are testing individual components of this system might run specifictypes of I/O requests to test out the performance or validate certain processing.
Known affectionately in the industry as the "four corners" test, because you can show them on a box, with writes on the left, reads on the right,hits on the top, and misses on the bottom.Engineers are proud of these results, but these workloads do notreflect any practical production workload. At best, since all I/O requests are oneof these four types, the four corners provide an expectation range from the worst performance (most often write-missin the lower left corner)and the best performance (most often read-hit in the upper right corner) you might get with a real workload.
To understand what is needed to design a test that is more reflective of real business conditions,let's go back to yesterday's discussion of fuel economy of vehicles, with mileage measured in miles per gallon.The How Stuff Works websiteoffers the following description for the two measurements taken by the EPA:
Why two different measurements? Not everyone drives in a city in stop-and-go traffic. Having only one measurement may not reflect the reality that you may travel long distances on the highway. Offering both city and highway measurements allows the consumers to decide which metric relates closer to their actual usage.
Should you expect your actual mileage to be the exact same as the standardized test?Of course not. Nobody drives exactly 11 miles in the city every morning with 23 stops along the way,or 10 miles on the highway at the exact speeds listed.The EPA's famous phrase "your mileage may vary" has been quickly adopted into popular culture's lexicon. All kinds of factors, like weather, distance, anddriving style can cause people to get better or worse mileage than thestandardized tests would estimate.
Want more accurate results that reflect your driving pattern, in specific conditions that you are most likely to drive in? You could rentdifferent vehicles for a week and drive them around yourself, keeping track of whereyou go, and how fast you drove, and how many gallons of gas you purchased, so thatyou can then repeat the process with another rental, and so on, and then use yourown findings to base your comparisons. Perhaps you find that your results are always20% worse than EPA estimates when you drive in the city, and 10% worse when you driveon the highway. Perhaps you have many mountains and hills where you drive, you drive too fast, you run the Air Conditioner too cold, or whatever.
If you did this with five or more vehicles, and ranked them best to worstfrom your own findings, and also ranked them best to worst based on the standardizedresults from the EPA, you likely will find the order to be the same. The vehiclewith the best standardized result will likely also have the best result from your ownexperience with the rental cars. The vehicle with the worst standardized result willlikely match the worst result from your rental cars.
(This will be one of my main points, that standardized estimates don't have to be accurate to beuseful in making comparisons. The comparisons and decisions you would make with estimatesare the same as you would have made with actual results, or customized estimates based on current workloads. Because the rankings are in the same order, they are relevant and useful for making decisions based on those comparisons.)
Most people shopping around for a new vehicle do not have the time or patience to do this with rental cars. Theycan use the EPA-certified standardized results to make a "ball-park" estimate on how much they will spendin gasoline per year, decide only on cars that might go a certain distancebetween two cities on a single tank of gas, or merely to provide ranking of thevehicles being considered. While mileage may not be the only metric used in making a purchase decision, it can certainly be used to help reduce your consideration setand factor in with other attributes, like number of cup-holders, or leather seats.
In this regard, the Storage Performance Council has developed two benchmarks that attempt to reflect normal business usage, similar to "City" and "Highway" driving measurements.
The SPC-2 benchmark was added when people suggested that not everyone runs OLTP anddatabase transactional update workloads, just as the "Highway" measurement was addedto address the fact that not everyone drives in the City.
If you are one of the customers out there willing to spend the time and resources to do your own performance benchmarking, either at your own data center, or with theassistance of a storage provider, I suspect most, if not all, the major vendors(including IBM, EMC and others), and perhaps even some of the smaller start-ups, would be glad to work with you.
If you want to gather performance data of your actual workloads, and use this to estimate how your performance might be with a new or different storage configuration, IBMhas tools to make these estimates, and I suspect (again) that most, if not all, of theother storage vendors have developed similar tools.
For the rest of you who are just looking to decide which storage vendors to invite on your next RFP, and which products you might like to investigate that matchthe level of performance you need for your next project or application deployment,than the SPC benchmarks might help you with this decision. If performance is importantto you, factor these benchmark comparisons with the rest of the attributes you arelooking for in a storage vendor and a storage system.
In my opinion, I feel that for some people, the SPC benchmarks provide some value in this decision making process. They are proportionally correct, in that even ifyour workload gets only a portion of the SPC estimate, that storage systems withfaster benchmarks will provide you better performance than storage systems with lower benchmark results. That is why I feel they can be relevant in makingvalid comparisons for purchase decisions.
Hopefully, I have provided enough "food for thought"on this subject to support why IBM participates in the Storage Performance Council, why the performance of the SAN Volume Controller can be compared to the performanceof other disk systems, and why we at IBM are proud of the recent benchmark results in our recent press release.
Enjoy the weekend!
technorati tags: IBM, SPC, EMC, Chuck Hollis, fastest, disk, system, SVC, HDD, storage, four corners, read-hit, read-miss, write-hit, write-miss, City, Highway, MPG, OLTP, SPC-1, SPC-2, benchmarks, file, database, video,[Read More]
Wrapping up my week's discussion on Business Continuity, I've had lots of interest in myopinion stated earlier this week that it is good to separate programs from data, and thatthis simplifies the recovery process, and that the Windows operating system can fit in a partition as small asthe 15.8GB solid state drive we just announced for BladeCenter. It worked for me, and I will use this post to show you how to get it done.
Disclaimer: This is based entirely on what I know and have experienced with my IBM Thinkpad T60 running Windows XP, and is meant as a guide. If you are running with different hardware or different operating system software, some steps may vary.
For this project, I have a DVD/CD burner in my Ultra-Bay, a stack of black CDs and DVDs, and a USB-attached 320GB external disk drive.
As with Business Continuity in the data center, planning in this manner can help you get back "up and running"quickly in the event of a disaster.
technorati tags: IBM, Business Continuity, Windows, XP, BladeCenter, solid, state, disk, backup, Linux, sysresccd, LiveCD, dd, gzip, split, Tivoli, Storage Manager, USB, Lotus Notes, NTFS, NTFS-3G, FAT32, primary, extended, logical, partition, magic, gparted[Read More]
Stephen2615 over at RupturedMonkey asksDo more SAN related issues happen with blade enclosures?and shares some of his bad experiences related to HP Blades in B class enclosures. Others comment that they had similar experiences with their B class equipment.
The question is if this is unique or specific to these particular models, or if this affects all kinds of blade servers because of their very nature and architecture. Stephen indicates that they also have HP C class enclosures, but since they are still in test mode, cannot comment on them.
I have no experience with any of HP's blade servers, but I have worked closely with our IBM BladeCenter team to help make sure that our storage, and our SAN equipment, work well together with the BladeCenter, and more importantly, that problems can be diagnosed effectively.
When I asked why people feel they need to know the inner workings of storage, the overwhelming response was to help diagnose problems. This could include problems inplacing related data on a potentially single point of failure, problems with performance, and problems communicating with 1-800-IBM-SERV.
So, if you have encountered problems diagnosing SAN problems with BladeCenter, or find that setting up an IBM SAN with blade servers in general, I would be interested in hearing what IBM can do to make the situation better.[Read More]
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Continuing our exploration this week into the performance of disk systems, today I will cover the metrics to measure performance. Why do people have metrics?
Several bloggers suggested that perhaps an analogy to vehicles would be reasonable, given that cars and trucks are expensive pieces of engineering equipment, and people make purchase decisions between different makes and models.
In the United States, the Environmental Protection Agency (EPA) government entity is responsible for measuringfuel economy of vehicles using the metric Miles Per Gallon (mpg).Specifically, these are U.S. miles (not nautical miles) and U.S. gallons, not imperial gallons. It is importantwhen defining metrics that you are precise on the units involved.
Since nearly all vehicles are driven by gallons of gasoline, and travel miles of distance, this is a great metric to use for comparing all kinds of vehicles, including motorcycles, cars, trucks and airplanes. The EPA has a fuel economy website to help people make these comp What about storage performance? What could we use as the "MPG"-like metric that would allow you to compare different makes and models of storage? The two most commonly used are I/O requests per second (IOPS) and Megabytes transferred per second (MB/s). To understand the difference in each one, let's go back to our analogy from yesterday's post. In this example, it might have only taken 1 second to actually provide the answer, but it might have taken 10-30 seconds to pick up the phone, hear the request, respond, and then hang up the phone. If one person is able to do this in 10 seconds, on average, then he can handle 360 questions per hour. If another person takes 30 seconds, then only 120 questions per hour. Many business applications read or write less than 4KB of information per I/O request, and as such the dominant factor is not the amount of time to transfer the data, but how quickly the disk system can respond to each request. IOPS is very much like counting "Questions handled per hour" at the public library. To be more specific on units, we may specify the specific block size of the request, say 512 bytes or 4096 bytes, to make comparisons consistent. Now suppose that instead of asking for something with a short answer, you ask the public library to read you the article from a magazine, identify all the movies and show times of a local theatre, or recite a work from Shakespeare. In this case, the time it took to pick up the phone and respond is very small compared to the time it takes to deliverthe information, and could be measured instead in words per minute. Some employees of the library may be faster talkers, having perhaps worked in auction houses in a prior job, and can deliver more words per minute than other employees. MB/s is very much like counting "Spoken words per minute" at the public library. To be more specific on units, we may request a specific amount of information, say the words contained in "Romeo and Juliet", to make comparisons consistent. Now that we understand the metrics involved, tomorrow we can discuss how to use these in the measurement process.
What about storage performance? What could we use as the "MPG"-like metric that would allow you to compare different makes and models of storage?
The two most commonly used are I/O requests per second (IOPS) and Megabytes transferred per second (MB/s). To understand the difference in each one, let's go back to our analogy from yesterday's post.
In this example, it might have only taken 1 second to actually provide the answer, but it might have taken 10-30 seconds to pick up the phone, hear the request, respond, and then hang up the phone. If one person is able to do this in 10 seconds, on average, then he can handle 360 questions per hour. If another person takes 30 seconds, then only 120 questions per hour. Many business applications read or write less than 4KB of information per I/O request, and as such the dominant factor is not the amount of time to transfer the data, but how quickly the disk system can respond to each request. IOPS is very much like counting "Questions handled per hour" at the public library. To be more specific on units, we may specify the specific block size of the request, say 512 bytes or 4096 bytes, to make comparisons consistent.
Now suppose that instead of asking for something with a short answer, you ask the public library to read you the article from a magazine, identify all the movies and show times of a local theatre, or recite a work from Shakespeare. In this case, the time it took to pick up the phone and respond is very small compared to the time it takes to deliverthe information, and could be measured instead in words per minute. Some employees of the library may be faster talkers, having perhaps worked in auction houses in a prior job, and can deliver more words per minute than other employees. MB/s is very much like counting "Spoken words per minute" at the public library. To be more specific on units, we may request a specific amount of information, say the words contained in "Romeo and Juliet", to make comparisons consistent.
Now that we understand the metrics involved, tomorrow we can discuss how to use these in the measurement process.
Continuing this week's theme on Business Continuity, I thought I would explore more on the identification of scenarios to help drive appropriate planning. As I mentioned in my last post, this should be done first.
A recent post in Anecdote talks about the long list of cognitive biases which affect business decision making. This list is a good explanation of why so many people have a difficult time identifying appropriate recovery scenarios as the basis for Business Continuity planning. Their "cognitive biases" get in the way.
Again, using my IBM Thinkpad T60 laptop as an example, here are a variety of different scenarios:
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For those in the US, a comedian named Carlos Mencia has a great TV show, Mind of Menciaand one of my favorite segments is "Why the @#$% is this news!" where he goes about showingblatantly obvious things that were reported in various channels.
So, when I saw that IBM once again, for the third year in a row, has the fastest disk system,the IBM System Storage SAN Volume Controller (SVC), based on widely-accepted industry benc
(Last year, I received comments fromWoody Hutsell, VP of Texas Memory Systems,because I pointed out that their "World's Fastest Storage"® cache-only system, was not as fast as IBM's SVC.You can ready my opinions, and the various comments that ensued, hereand here. )
That all changed when EMC uber-blogger Chuck Hollis forgot his own Lessons in Marketingwhen heposted his rantDoes Anyone Take The SPC Seriously?That's like asking "Does anyone take book and movie reviews seriously?" Of course they do!In fact, if a movie doesn't make a big deal of its "Two thumbs up!" rating, you know it did not sitwill with the reviewers. It's even more critical for books. I guess this latest news from SPC reallygot under EMC's skin.
For medium and large size businesses, storage is expensive, and customers want to do as much research as possible ahead of time to make informed decisions. A lot of money is at stake, and often, once you choose a product, you are stuckwith that vendor for many years to come, sometimes paying software renewals after only 90 days, and hardware maintenance renewals after only a year when the warranty runs out.
Customers shopping for storage like the idea of a standardized test that is representative, so they can compare one vendor's claims with another. The Storage Performance Council (SPC), much like the Transaction Processing Performance Council (TPC-C) for servers, requires full disclosure of the test environment so people can see what was measured and make their own judgement on whether or not it reflects their workloads. Chuck pours scorn on SPC but I think we should point to TPC-C as a great success story and ask why he thinks the same can't happen for storage? Server performance is also a complicatedsubject, but people compare TPC-C and TPC-H benchmarks all the time.
Note: This blog post has been updated. I am retracting comments that were unfair generalizations. The next two paragraphs are different than originally posted.
Chuck states that "Anyone is free, however, to download the SPC code, lash it up to their CLARiiON, and have at it." I encourage every customer to do this with whatever disk systems they already have installed. Judge for yourself how each benchmark compares to your experience with your application workload, and consider publishing the results for the benefit of others, or at least send me the results, so that I can understand better all of these"use cases" that Chuck talks about so often. I agree that real-world performance measurements using real applications and real data are always going to be more accurate and more relevant to that particular customer. Unfortunately, there are little or no such results made public. They are noticeably absent. With thousands of customers running with storage from all the major storage vendors, as well as storage from smaller start-up companies, I would expect more performance comparison data to be readily available.
In my opinion, customers would benefit by seeing the performance results obtained by others. SPC benchmarks help to fill this void, to provide customers who have not yet purchased the equipment, and are looking for guidance of which vendors to work with, and which products to put into their consideration set.
Truth is, benchmarks are just one of the many ways to evaluate storage vendors and their products. There are also customer references, industry awards, and corporate statements of a company's financial health, strategy and vision.Like anything, it is information to weigh against other factors when making expensive decisions. And I am sure the SPC would be glad to hear of any suggestions for a third SPC-3 benchmark, if the first two don't provide you enough guidance.
So, if you are not delighted with the performance you are getting from your storage now, or would benefit by having even faster I/O, consider improving its performance by adding SAN Volume Controller. SVC is like salt or soy sauce, it makes everything taste better. IBM would be glad to help you with a try-and-buy or proof-of-concept approach, and even help you compare the performance, before and after, with whatever gear you have now. You might just be surprised how much better life is with SVC. And if, for some reason, the performance boost you experience for your unique workload is only 10-30% better with SVC, you are free to tell the world about your disappointment.
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Continuing this week's theme on Business Continuity, I will use this post to discuss this week'sIBM solid state disk announcement.This new offering provides a new way to separate programs from data, to help minimizedowntime and outages normally associated with disk drive failures.
Until now, the method most people used to minimize the amount of data on internalstorage was to use disk-less servers with Boot-Over-SAN, however, not all operating systems, and not all disk systems, supported this.
Windows, however, is not supported, because of the small 4GB size and USB protocol limitations. For Windows, you would add a SAS drive, you boot from this hard drive, and use the 4GB Flash drive for data only.
So what's new this time? Here's a quick recap of July 17 announcement. For the IBM BladeCenter HS21 XM blade servers, new models of internal "disk" storage:
Until recently, solid state storage was available at a price premium only. Flash prices have dropped 50% annually while capacities have doubled. This trend is expected to continue through 2009.
Flash drives use non-volatile memory instead of moving parts, so less likely to break down during high external environmental stress conditions, like vibration and shock, or extreme temperature ranges (-0C° to +70°C) that would make traditional hard disks prone to failure.This is especially important for our telecommunications clients, who are always looking for solutions that are NEBS Level 3 compliant.
Last year, I mentioned that flash drives could provide only a limited number of write and erase cycles, but today's new advances in wear-leveling algorithms have nearly eliminated this limitation.
As with any SATA drive, performance depends on workload.Solid state drives perform best as OS boot devices, taking only a few secondslonger to boot an OS than from a traditional 73GB SAS drive. Flash drives also excel in applications featuring random read workloads, such as web servers. For random and sequential write workloads, use SAS drives instead for higher levels of performance.
So, even though this is not part of the System Storage product line, I am very excitedfor IBM. To find out if this will work in your environment, go to the IBM Server Provenwebsite that lists compatability with hardware, applications and middleware, or review the latest Configuration and Options Guide (COG).
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It's Tuesday, which means IBM makes its announcements. We had several for the IBM System Storage product line. Here's a quick recap.
I'm off to Denver, Colorado this week. I hope it is cooler there than it is down here in Tucson, Arizona.
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