Inside System Storage -- by Tony Pearson

I mean, seriously, who else but someone who's already implemented thin provisioning would really understand the implications of "chunk" size enough to care?

For those of you who don't know what the heck "chunk size" means (now listen up you folks over at IBM who have yet to implement thin provisioning on your own storage products), a "chunk" is the term used (and I think even trademarked by 3PAR) to refer to the unit of actual storage capacity that is assigned to a thin device when it receives a write to a previously unallocated region of the device.

For reference, Hitachi USP-V uses I think a 42MB chunk, XIV NEXTRA is definitely 1MB, and 3PAR uses 16K or 256K (depending upon how you look at it).

Thin Provisioning currently offered in IBM System Storage N serieswas technically "implemented" by NetApp, and that the Thin Provisioning that will be offered in our IBM XIV Nextrasystems will have been acquired from XIV. Lest I remind you that many of EMC's products were developed by other companies first, then later acquired by EMC, so no need for you to throw rocks from your glass houses in Hopkington.

"Thin provisioning" was first introduced by StorageTek in the 1990's and sold by IBM under the name of RAMAC Virtual Array (RVA). An alternative approach is "Dynamic Volume Expansion" (DVE). Rather than giving the host application a huge 2TB LUN but actually only use 50GB for data, DVE was based on the idea that you only give out 50GB they need now, but could expand in place as more space was required. This was specifically designed to avoid the biggest problem with "Thin Provisioning" which back then was called "Net Capacity Load" on the IBM RVA, but today is now referred to as "over-subscription". It gave Storage Administrators greater control over their environment with no surprises.

In the same manner as Thin Provisioning, DVE requires a "chunk size" to work with. Let's take a look:

DS4000 series

On the DS4000 series, we use the term "segment size", and indicate that the choice of a segment size can have some influence on performance in both IOPS and throughput. Smaller segment sizes increase the request rate (IOPS) by allowing multiple disk drives to respond to multiple requests. Large segment sizes increase the data transfer rate(Mbps) by allowing multiple disk drives to participate in one I/O request. The segment size does not actually change what is stored in cache, just what is stored on the disk itself.It turns out in practice there is no advantage in using smaller sizes with RAID 1; only in a few instances does this help with RAID-5 if you can writea full stripe at once to calculate parity on outgoing data. For most business workloads, 64KB or 128KB are recommended. DVE expands by the same number of segments across all disks in the RAID rank, so for example in a 12+P rank using 128KB segment sizes, the chunk size would be thirteen segments, about 1.6MB in size.

SAN Volume Controller

On the SAN Volume Controller, we call this "extent size" and allow it to be various values 64MB to 512MB. Initially,IBM only managed four million extents, so this table was used to explain the maximum amount that could be managedby an SVC system (up to 8 nodes) depending on extent size selected.

Extent Size	Maximum Addressable
16MB	64TB
32MB	128TB
64MB	256TB
128MB	512TB
256MB	1PB
512MB	2PB

IBM thought that since we externalized "segment size" on the DS4000, we should do the same for the SANVolume Controller. As it turned out, SVC is so fast up in the cache, that we could not measure any noticeable performance difference based on extent size. We did have a few problems. First, clients who chose 16MB andthen grew beyond the 64TB maximum addressable discovered that perhaps they should have chosen something larger.Second, clients called in our help desk to ask what size to choose and how to determine the size that was rightfor them. Third, we allowed people to choose different extent sizes per managed disk group, but that preventsmovement or copies between groups. You can only copy between groups that use the same extent size. The generalrecommendation now is to specify 256MB size, and use that for all managed disk groups across the data center.

The latest SVC expanded maximum addressability to 8PB, still more than most people have today in their shops.

DS8000 series

Getting smarter each time we introduce new function, we chose 1GB chunks for the DS8000. Based on a mainframebackground, most CKD volumes are 3GB, 9GB, or 27GB in size, and so 1GB chunks simplified this approach. Spreadingthese 1GB chunks across multiple RAID ranks greatly reduced hot-spots that afflict other RAID-based systems.(Rather than fix the problem by re-designing the architecture, EMC will offer to sell you software to help you manually move data around inside the Symmetrix after the hot-spot is identified)

Unlike EMC's virtual positioning, IBM DS8000 dynamic volume expansion does work on CKD volumes for our System z mainframe customers.

The trade-off in each case was between granularity and table space. Smaller chunks allow finer control on the exact amount allocated for a LUN or volume, but larger chunks reduced the number of chunks managed. With our advanced caching algorithms, changes in chunk size did not noticeably impact performance. It is best just to come up with a convenient size, and either configure it as fixed in the architecture, or externalize it as a parameter with a good default value.

Meanwhile, back at EMC, BarryB indicates that they haven't determined the "optimal" chunk size for their newfunction. They plan to run tests and experiments to determine which size offers the best performance, and thenmake that a fixed value configured into the DMX-4. I find this funny coming from the same EMC that won't participate in [standardized SPC benchmarks] because they feel that performance is a personal and private matter between a customer and their trusted storage vendor, that all workloads are different, and you get the idea. Here's another excerpt:

Back at the office, they've taking to calling these "chunks" Thin Device Extents (note the linkage back to EMC's mainframe roots), and the big secret about the actual Extent size is...(wait for it...w.a.i.t...for....it...)...the engineers haven't decided yet!

That's right...being the smart bunch they are, they have implemented Symmetrix Virtual Provisioning in a manner that allows the Extent size to be configured so that they can test the impact on performance and utilization of different sizes with different applications, file systems and databases. Of course, they will choose the optimal setting before the product ships, but until then, there will be a lot of modeling, simulation, and real-world testing to ensure the setting is "optimal."

Finally, BarryB wraps up this section poking fun at the chunk sizes chosen by other disk manufacturers. I don't knowwhy HDS chose 42MB for their chunk size, but it has a great[Hitchiker's Guide to the Galaxy]sound to it, answering the ultimate question to life, the universe and everything. Hitachi probably went to theirDeep Thought computer and asked how big should their "chunk size" be for their USP-V, and the computer said: 42.Makes sense to me.

I have to agree that anything smaller than 1MB is probably too small. Here's the last excerpt:

Now, many customers and analysts I've spoken to have in fact noted that Hitachi's "chunk" size is almost ridiculously large; others have suggested that 3PAR's chunks are so small as to create performance problems (I've seen data that supports that theory, by the way).

Well, here's the thing: the "right" chunk size is extremely dependent upon the internal architecture of the implementation, and the intersection of that ideal with the actual write distribution pattern of the host/application/file system/database.

So my suggestion to EMC is, please, please, please take as much time as you need to come up with the perfect"chunk size" for this, one that handles all workloads across a variety of operating systems and applications, from solid-state Flash drives to 1TB SATA disk. Take months or years, as long as it takes. The rest of the world is in no hurry, as thin provisioning or dynamic volume expansion is readily available on most other disk systems today.

Maybe if you ask HDS nicely, they might let you ask their computer.

technorati tags: IBM, thin provisioning, XIV, Nextra, N series, chunk size, BarryB, EMC, Symmetrix, virtual provisioning, 3PAR, Hitachi, HDS, USP-V, StorageTek, RAMAC Virtual Array, RVA, dynamic volume expansion, DVE, 42MB, Hitchhiker's Guide, CKD, System z, mainframe, SATA, DS8000, DS4000, SAN Volume Controller, SVC

(Disclaimer: IBM has a strong working relationship with Apple, and manufacturers technology used in someof Apple's products. I own both an Apple iPod as well as an Apple G4 Mac Mini. IBM supports its employees usingApple laptops instead of Windows-based ones for work, and IBM has developed software that runs on Apple's OS X.Apple is kind enough to extend its "employee discount prices" to IBM employees.)

[Apple OS X 10.5 Leopard operating system]

In the first 90 days of its release, Apple sold 5 million copies, representing 19 percent of Mac users. I am stillone of the 81 percent still using 10.4 Tiger, the previous level. My Mac Mini is based on G4 POWER processor, and upgrading is on my [Someday/Maybe] list. I am not taking sides in the [OS X vs. Windows vs. Linux religious debate]; I use all three.

The key storage-related feature of Leopard is their backup software Time Machine, and Steve Jobs announceda companion product called Time Capsule that would serve as the external backup disk wirelessly, over 802.1nWi-Fi. For many households, backup is either never done, or done rarely, so any help to simplify and relieve theburden is welcome.

Time Capsule comes in 500GB and 1TB SATA disk capacities, which Steve Jobs called "server-grade". What about a 750GB model? Looks like Apple followed EMC'sexample and went straight to 1TB instead. After EMC failed to deliver 750GB drives in 2007 that they [promised back in July], EMC blogger Chuck Hollis explains in his post[Enterprise Storage Strikes Back!]:

So there's something in the EMC goodie bag as well for you -- the availability of the new 1TB disk drives you've been hearing about. We skipped the 750GB drive and went right to the 1TB drive.

Apple iPhone and iPod Touch

In the first 200 days, Apple has sold 4 million phones, and has garnered nearly 20 percent of the smart phone market share. New features include a GPS-like location feature that uses [triangulation] with cell phone towers and Wi-Fi hotspotsto determine where you are located.

I covered last year's introduction of the iPhone in my post on [Convergence].All of the features he presented were software updates to the existing 8GB and 16GB models. No new modelswith larger storage were introduced.

I am a T-mobile customer, so am out of luck until either (a) Apple unlocks their phones from the AT&T network, or(b) Apple signs an agreement with T-mobile in the USA. I reviewed the various hacks to unlock iPhones last year, but was not interested in losing official warranty or future software support.

The iPod Touch is an interesting alternative. It is basically an iPhone with the cell-phone features disabled, whichgives you Wi-Fi over the Safari browser, music, videos, and so on. Steve Jobs mentioned enhanced software updates for this as well. The iPod Touch comes in the same 8GB and 16GB sizes as the iPhone.

AppleTV and iTunes

Steve Jobs indicated that they have sold over 4 billion songs over iTunes, 125 million TV shows, and 7 million movies.He announced that now iTunes would allow for movie rentals, with the option to see them within 30 days, but once you started watching a movie, you have 24 hours to finish. I found it interesting that he said rentals were to reduce space on your hard drive, versus outright purchase of movie content.

In a rare concession, Steve admitted that the original AppleTV misunderstood the marketplace. The original AppleTV allowed you to view pictures and listen to music through your television, but people wanted to view movies. Thesoftware upgrade would allow this, using the iTunes rental model above, as well as watch video podcasts and over 50 million videos posted on YouTube.

Some television-related stats from [z/Journal] were quite timely. The older non-digital TVs could be usedwith the AppleTV and gaming systems like Nintendo Wii.

• 33 percent of U.S. households do not know what to do with (their older) TVs after digital switch (Feb 2009)
• 69 percent of Americans think PCs are more entertaining than TV

Rather than try to fight peer-to-peer website piracy, Apple cleverly decided to compete head-to-head against it. This iswell summarized in Matt Mason's 6-minute video [The Pirate's Dilemma]. Eleven major movie studios are on board with Apple's movie rental plans, making thousands of movietitles available for this, with hundreds in High Definition (HD).

I personally have a Tivo, connected wirelessly to a regular non-HD television, as well as my PC, Mac and internet hub, and this allows me to view my photos, listen to my iTunes collection of music and internet radio stations from [Live365], as well as rent movies and TV shows from Amazon Unbox, with prices ranging from free to four dollars.

MacBook Air

The theme of this week was "Something is in the Air", an obvious reference to this product, billed as the world's thinnest laptop.John Windsor on his YouBlog writes[Making it Memorable] aboutthe use of a standard office envelope to demonstrate how thin this new MacBook Air laptop is. It is 0.16 inchesat one end, and 0.76 inches as the other end. Unlike other "ultra-thin" laptops, this has a full-size back-lit keyboardand full-size 13.3 inch widescreen. The touchpad supports multi-touch gestures similar to the iPhone and iPod Touch.Intel managed to shrink down their Core 2 Duo processor chip by 60 percent to fit inside this machine. Thebattery is reported to last five hours.

This laptop was designed for wireless access, with 802.1n and BlueTooth enabled. No RJ-45 connection for traditionalLAN ethernet connection, but I guess you can use a USB-to-RJ45 converter.

Storage-wise, you can choose between the 1.8-inch 80GB HDD or a pricey-but-faster 64GB Flash Solid-State Disk (SSD).In a move similar to [getting rid of the 3.5-inch floppy disk in 1998's iMac G3], the MacBook Air got rid of the CD/DVDdrive. While they offer a USB-attachable SuperDrive as an optional peripheral, Steve Jobs gave alternative methods:

Before	After
Watching movies on DVD	Rent or Buy from iTunes instead
Burning music CDs for your car stereo	Attach your iPod to your car stereo
Taking backups to CD or DVD	Use Time Machine and Time Capsule instead
Installing Software from CD	Wirelessly connect to a "Remote Optical Disc" on a Mac or PC, running special Apple-provided software that allows you to make this connection

Here's a list to the 90-minute[keynote address video]. If you arenot a fan of recycling, saving the environment, free speech or democracy, you can safely skip the last 15 minutes when musical artist Randy Newman performs.For alternative viewpoints on the keynote, see posts from [John Gruber] and [Tara MacKay].

technorati tags: Apple, MacWorld, IBM, OS X, Leopard, Tiger, iPod, Mac Mini, G4, Time Machine, Time Capsule, 500GB, 1TB, SATA, EMC, Chuck Hollis, 750GB, 802.1n, Wi-Fi, iPhone, iPod Touch, T-mobile, unlock, AppleTV, iTunes, movie rentals, Tivo, Amazon, Unbox, Live365, John Windsor, YouBlog, MacBook Air, Flash, SSD, BlueTooth, Remote Disc, CD/DVD drive, iMac, G3, John Gruber, Randy Newman, Tara MacKay, recycling, environment, free speech, democracy, HD, piracy, Matt Mason

Now the casinos have people trained, like chickens hoping for pellets, to take money from one machine (the ATM), carry it across a room and deposit in another machine (the slot machine). I believe B.F. Skinner would agree with me that there is room for even more efficiency: The ATM and the slot machine need to be the same machine.

The casinos lose a lot of money waiting for the portly gamblers with respiratory issues to waddle from the ATM to the slot machines. A better solution would be for the losers, euphemistically called “players,” to stand at the ATM and watch their funds be transferred to the hotel, while hoping to somehow “win.” The ATM could be redesigned to blink and make exciting sounds, so it seems less like robbery.

I’m sure this is in the five-year plan. Longer term, people will be trained to set up automatic transfers from their banks to the casinos. People will just fly to Vegas, wander around on the tarmac while the casino drains their bank accounts, then board the plane and fly home. The airlines are already in on this concept, and stopped feeding you sandwiches a while ago.

Perhaps EMC can redesign its DMX-4 to "blink and make exciting sounds" as well. The Flash Drives were designedfor the financial services industry, so those disk systems could be directly connected to make transfers between the appropriate bank accounts.

technorati tags: Scott Adams, Dilbert, B.F. Skinner, ATM, casinos, EMC, DMX-4

A young carpenter immigrates to the United States from Italy, unable to speak a word of English. Upon arrival, he moves into a small apartment by himself and begins looking for a job in construction. With some luck and a lot of hard work, he quickly lands a job at a local construction site. Over the coming weeks he learns how to say “hello” and “goodbye” to his English-only coworkers. As time goes on, he is able to learn more complex phrases and commands and is now able to begin taking on jobs that better match his level of expertise.

Several years after the carpenter moved to the US, he now speaks fluent English and has started a family with an American woman and now speaks only English on the job site and at home. One afternoon, while hammering at the framing of a new home, the carpenter strikes his thumb. In what language does he curse?Italian, of course.

We believe that this story illustrates the nature of reacting to difficult, stressful, and, yes, painful situations by reverting to what you know best. This is the reason that coaches ask their players to make certain actions “instinctual” – simply, when times get tough, we do what we fall back on our native language.

Last September, in my post[Supermarketsand Specialty Shops] I mentioned how Forrester Research identified two kinds of IT vendors selling storage. On one side were the"information infrastructure" companies (IBM, HP, Sun, and Dell) that focus on providing one-stop shopping for clients that want all parts of an IT solution, including servers, storage, software and services. These I compared to "supermarkets".

On the other side were the storage component vendors (EMC, HDS, NetApp, and many others) that focus on specificstorage components. These I compared to "specialty shops", like butchers, bakers and candlestick makers.These often appeal to customers with big enough IT staffs with the skills to do their own system integration.The key difference seems to be that the supermarkets are client-focused, and the specialty shops are technology-focused, and different people prefer to do business with one side or another.This came in handy last November to explain Dell's acquisition of EqualLogic and discuss[IBMEntry-Level iSCSI offerings].

Some recent news seems to fit this model, in relation to the Native Language Theory.

EMC

Several argued that EMC was in the process of shifting sides, from disk specialty shop over to an everything-but-servers supermarket. Certainly many of its acquisitions in software, services, and VMwarewould support the notion that perhaps they are going through an identity crisis.The immediate beneficiary was HDS, the #2 disk specialty shop, that passedup EMC with innovative features in its USP-V disk system.

However, times are tough, especially in the U.S. economy that many storage vendors are focused on. EMCappears to have found its native language, going back to its roots of solid state storage systems thatthey started with back in 1979. This week EMC announced [Symmetrix DMX-4 support of Flash drives].Several bloggers review the technology involved:

• Chuck Hollis [Enterprise Storage Strikes Back]
• Storage Anarchist [Bold, Fast, Green]
• StorageZilla [Enterprise Flash for DMX-4]
• Stephen Foskett [Flash! EMC's DMX is the new thing again]

Overall smart move for EMC to go back to its technology-focused disk specialty shop mode and go head-to-head against the HDS threat. With Web 2.0 workloads moving off these monolithic solutions and onto [clustered storage more appropriate for "cloud computing"], large enterprise-class disk systems like theIBM System Storage DS8000 and EMC DMX-4 can shift focus on what they do best: online transaction processing (OLTP) and large databases. However,I noticed the EMC press release mentions EMC as an "information infrastructure" company, so perhaps they stillhaven't resolved their identity crisis.

(For the record, IBM shipped [Flash drive-based storage last year], and announced [larger drive models] this week. As we have learned from last year, terms like "First" or "Leader" in corporate press releases should not always be taken literally.)

Sun Microsystems

After Sun acquired StorageTek specialty shop, they too had a bit of an identity crisis.Fortunately, they realized their core strengths were on the "supermarket" side,moved storage in with servers in their latest restructuring, changed their NYSE symbol from SUNW to JAVA, and reset their focus on providing end-to-end solutions like IBM. For example, fellow blogger Taylor Allis from Sun mentions their latest in "clustered storage" in his post[IBM Buys XIV - Good Move].

Last August, in my post [Fundamental Changes for Green Data Centers], I mentioned that IBM consolidated 3900 rack-optimized servers onto 33 mainframes,and that this was part of our announcement that[since 1997, IBM has consolidated its strategic worldwide data centers from 155 to seven].I noticed in Nick Carr's Rough Type blog post[The Network is the Data Center] thatHP and Sun have followed suit:

In an ironic twist, some of today's leading manufacturers of server computers are also among the companies moving most aggressively to reduce their need for servers and other hardware components. Hewlett-Packard, for instance, is in the midst of a project to slash the number of data centers it operates from 85 to 6 and to cut the number of servers it uses by 30 percent. Now, Sun Microsystems is upping the stakes. Brian Cinque, the data center architect in Sun's IT department, says the company's goal is to close down all its internal data centers by 2015. "Did I just say 0 data centers?" he writes on his blog."Yes! Our goal is to reduce our entire data center presence by 2015."

While Nick feels this is ironic for Sun, known for UNIX servers based on their SPARC chip technology, I don't. Sun has shifted from being technology-focused to being client-focused.This is where the marketplace is going, and the supermarket vendors, being client-focused, are best positioned to adapt to this new world. In a sense, Sun found its roots. Nick summarizes this as:"The network, to spin the old Sun slogan, becomes the data center."

So, each move seems to strengthen their respective identities back to their origins, or at least help them communicate that to the market.

technorati tags: core strengths, native language, Forrester Research, supermarket, specialty shops, IBM, HP, Sun, Dell, information infrastructure, client-focused, technology-focused, EqualLogic, EMC, HDS, NetApp, USP-V, DMX-4, Flash, disk, drive, systems, Java, Taylor Allis, UNIX, SPARC, Nick Carr