Tony Pearson is a Master Inventor and Senior IT Architect for the IBM Storage product line at the
IBM Systems Client Experience Center in Tucson Arizona, and featured contributor
to IBM's developerWorks. In 2016, Tony celebrates his 30th year anniversary with IBM Storage. He is
author of the Inside System Storage series of books. This blog is for the open exchange of ideas relating to storage and storage networking hardware, software and services.
(Short URL for this blog: ibm.co/Pearson )
My books are available on Lulu.com! Order your copies today!
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It's official! My "blook" Inside System Storage - Volume I is now available.
This blog-based book, or “blook”, comprises the first twelve months of posts from this Inside System Storage blog,165 posts in all, from September 1, 2006 to August 31, 2007. Foreword by Jennifer Jones. 404 pages.
IT storage and storage networking concepts
IBM strategy, hardware, software and services
Disk systems, Tape systems, and storage networking
Storage and infrastructure management software
Second Life, Facebook, and other Web 2.0 platforms
IBM’s many alliances, partners and competitors
How IT storage impacts society and industry
You can choose between hardcover (with dust jacket) or paperback versions:
This is not the first time I've been published. I have authored articles for storage industry magazines, written large sections of IBM publications and manuals, submitted presentations and whitepapers to conference proceedings, and even had a short story published with illustrations by the famous cartoon writer[Ted Rall].
But I can say this is my first blook, and as far as I can tell, the first blook from IBM's many bloggers on DeveloperWorks, and the first blook about the IT storage industry.I got the idea when I saw [Lulu Publishing] run a "blook" contest. The Lulu Blooker Prize is the world's first literary prize devoted to "blooks"--books based on blogs or other websites, including webcomics. The [Lulu Blooker Blog] lists past year winners. Lulu is one of the new innovative "print-on-demand" publishers. Rather than printing hundredsor thousands of books in advance, as other publishers require, Lulu doesn't print them until you order them.
I considered cute titles like A Year of Living Dangerously, orAn Engineer in Marketing La-La land, or Around the World in 165 Posts, but settled on a title that matched closely the name of the blog.
In addition to my blog posts, I provide additional insights and behind-the-scenes commentary. If you go to the Luluwebsite above, you can preview an entire chapter in its entirety before purchase. I have added a hefty 56-page Glossary of Acronyms and Terms (GOAT) with over 900 storage-related terms defined, which also doubles as an index back to the post (or posts) that use or further explain each term.
So who might be interested in this blook?
Business Partners and Sales Reps looking to give a nice gift to their best clients and colleagues
Managers looking to reward early-tenure employees and retain the best talent
IT specialists and technicians wanting a marketing perspective of the storage industry
Mentors interested in providing motivation and encouragement to their proteges
Educators looking to provide books for their classroom or library collection
Authors looking to write a blook themselves, to see how to format and structure a finished product
Marketing personnel that want to better understand Web 2.0, Second Life and social networking
Analysts and journalists looking to understand how storage impacts the IT industry, and society overall
College graduates and others interested in a career as a storage administrator
And yes, according to Lulu, if you order soon, you can have it by December 25.
Yesterday, I promised I would cover other products from the Feb 12 announcement. Today I will focus on the IBM SAN768B director. Some people are confused on the differences between switchesand directors. I find there are three key differences:
Directors are designed to be 24x7 operation, highly available with no single points of failure or repair. Generally, all components in directors are redundant and hot-swappable, including Control Processors. In switches, some components are redundant and hot-swappable, such as fans and power supplies), but not the “motherboard” or controller. Often you have to take down a switch to make firmware or major hardware changes or upgrades.
Directors are designed to take in "blades" with different features, port counts, or protocol capabilities. You can add or remove blades while the system is up and running. Switches have a fixed number of ports. (A Small Form-factor Pluggable optical transceiver [SFP] is the component that turns electric pulses into light pulses (and visa versa). You plug the SFP into the switch, and then the fiber optic cable is plugged into the SFP).
With switches, you often start with a base number of active ports, and then can enable the rest of the ports as you need them.
Directors have hundreds of ports. Switches tend to have 64 ports or less.
Last year, Brocade acquired McDATA. Both were OEMs for IBM, and IBM distinguished that in the naming convention. The IBM SAN***B name was used to denote products manufactured for IBM by Brocade, and a SAN***M name was used to denote products manufactured by McDATA.
At that time, Brocade and McDATA equipment did not mix very well on the same fabric, so IBM retained the naming convention so that you as a customer knew what it worked with.
Brocade now has released with new levels of both operating systems--Brocade's FOS and McDATA's EOS--and their respective fabric managers--Brocade Fabric Manager (FM) and McDATA's Enterprise Fabric Connectivity Manager (EFCM)--so that they have full interoperability.
Brocade's goal is to enhance EFCM to be a common software management platform for all of their products going forward.
IBM used the maximum port count in the name to provide some clue as to the size of the switch or director. The SAN16B-2 or the SAN32B-3 are switches that have a maximum of 16 and 32 ports. The SAN256B supports a maximumeight blades of your choosing.Two different types were supported for FC ports, a 16-port blade and a 32-port blade.If all eight were 32-port blades then the maximum was 256 ports, hence the name. But then Brocade began offering 48-port blades. Should IBM change the name? No, it decided to leave itthe SAN256B even though it can now have a maximum of 384 ports.
Not to confuse anyone, the SAN768B also has a maximum of 384 ports, in the same 14U dimensions, but with a special twist. Normally to connect two directors together you use up ports from each, in what are called "inter-switch links" (ISL).These are ports you are taking away from availability from the servers and storage controllers. The SAN768Boffers a new alternative called "inter-chassis links". Each SAN768B has two processing blades, and each has two ICL ports, so with just four two-meter (2m) cables, you get the equivalent of 128 FC 8 Gbps ISL links without using 128 individual ports on each side. That is like giving you 256 ports back for use with servers and storage!
Since IBM directors require 240 volt power, IBM TotalStorage SAN Cabinet C36 include power distribution units (PDUs). PDUs are just glorified power strips, but a new intelligent PDU (iPDU) option introduces additional intelligence to monitor energy consumption for customers looking to measure, and perhaps charge back, energy consumption to the rest of the business. You can stack two SAN768B in one cabinet, one on top of the other, and connected via ICLs, it wouldlook like one huge 768-port backbone.
As a backbone for your data center, the SAN768B is positioned for two emerging technologies:
8 Gbps Fibre Channel (FC)
The SAN768B is powerful enough to have 32-port blades run full speed on all ports off-blade without oversubscription. Oversubscription is an emotional topic.
Normally, blades (like switches) can handle all traffic at full speed without delays provided the in-bound and out-bound ports involved are all on the same blade. In a director, however, if you need to communicate from a port on one blade to a port on a different blade, it is possible that off-blade traffic might be constrained or delayed in its transit across the backplane.
On the SAN768B, both the 16-port and 32-port blades can run at full 8 Gbps speed, and the 48-port is exposed to oversubscription only if you have more than 32-ports running at full 8 Gbps transferring data off-blade concurrently.
The new 8 Gbps SFPs support auto-negotiation at N-1 and N-2 generation link speeds. This means that they will automatically slow down when communicating with 4Gpbs and 2 Gbps devices, but they cannot communicate with 1 Gbps devices. If you are still using 1 Gbps devices in your data center, you will need to use 4 Gbps SFPs (which also support 2 Gbps and 1 Gbps link speeds) to communicate with those older devices.
Basically, this new technology enables transport of Fibre Channel packets over 10 Gbps Ethernet links. This 10 Gbps Ethernet can also be used to carry traditional iSCSI and TCP/IP traffic. FCoE introduces new extensions to provide Fibre Channel characteristics, like being lossless, and offering consistent performance. The ANSI T11 team is driving FCoE as an open standard, and at the moment it is not fully baked. I suggest you don't buy any FCoE equipment prematurely, as pre-standard devices or host bus adapters could get you burned later when the standard is finalized.
The idea is that FCoE blades can be installed in a SAN768B along with traditional FC blades, allowing routing of traffic between traditional FC and new FCoE ports. Those who have invested in FCIP for long distance replication will be able to continue using either FC or FCoE inputs.
One of the big drivers of FCoE is IBM BladeCenter. Currently, most BladeCenter blades support both Ethernet and FC connectivity and are connected to both Ethernet and FC switches on the back of each BladeCenter chassis. With FCoE, we have the potential to run both FC and IP traffic across simpler all-Ethernet blades, connecting through all-Ethernet switches on the backs of each chassis.
For more information on the IBM SAN768B, see the [IBM Press Release]. For more detailson Brocade's strategy, here is an 8-page white paper on their[Data Center Fabric] vision.
While most of the post is accurate and well-stated, two opinions particular caught my eye. I'll be nice and call them opinions, since these are blogs, and always subject to interpretation. I'll put quotes around them so that people will correctly relate these to Hu, and not me.
"Storage virtualization can only be done in a storage controller. Currently Hitachi is the only vendor to provide this." -- Hu Yoshida
Hu, I enjoy all of your blog entries, but you should know better. HDS is fairly new-comer to the storage virtualization arena, so since IBM has been doing this for decades, I will bring you and the rest of the readers up to speed. I am not starting a blog-fight, just want to provide some additional information for clients to consider when making choices in the marketplace.
First, let's clarify the terminology. I will use 'storage' in the broad sense, including anything that can hold 1's and 0's, including memory, spinning disk media, and plastic tape media. These all have different mechanisms and access methods, based on their physical geometry and characteristics. The concept of 'virtualization' is any technology that makes one set of resources look like another set of resources with more preferable characteristics, and this applies to storage as well as servers and networks. Finally, 'storage controller' is any device with the intelligence to talk to a server and handle its read and write requests.
Second, let's take a look at all the different flavors of storage virtualization that IBM has developed over the past 30 years.
IBM introduces the S/370 with the OS/VS1 operating system. "VS" here refers to virtual storage, and in this case internal server memory was swapped out to physical disk. Using a table mapping, disk was made to look like an extension of main memory.
IBM introduces the IBM 3850 Mass Storage System (MSS). Until this time, programs that ran on mainframes had to be acutely aware of the device types being written, as each device type had different block, track and cylinder sizes, so a program written for one device type would have to be modified to work with a different device type. The MSS was able to take four 3350 disks, and a lot of tapes, and make them look like older 3330 disks, since most programs were still written for the 3330 format. The MSS was a way to deliver new 3350 disk to a 3330-oriented ecosystem, and greatly reduce the cost by handling tape on the back end. The table mapping was one virtual 3330 disk (100 MB) to two physical tapes (50 MB each). Back then, all of the mainframe disk systems had separate controllers. The 3850 used a 3831 controller that talked to the servers.
IBM invents Redundant Array of Independent Disk (RAID) technology. The table mapping is one or more virtual "Logical Units" (or "LUNs") to two or more physical disks. Data is striped, mirrored and paritied across the physical drives, making the LUNs look and feel like disks, but with faster performance and higher reliability than the physical drives they were mapped to. RAID could be implemented in the server as software, on top or embedded into the operating system, in the host bus adapter, or on the controller itself. The vendor that provided the RAID software or HBA did not have to be the same as the vendor that provided the disk, so in a sense, this avoided "vendor lock-in".Today, RAID is almost always done in the external storage controller.
IBM introduces the Personal Computer. One of the features of DOS is the ability to make a "RAM drive". This is technology that runs in the operating system to make internal memory look and feel like an external drive letter. Applications that already knew how to read and write to drive letters could work unmodified with these new RAM drives. This had the advantage that the files would be erased when the system was turned off, so it was perfect for temporary files. Of course, other operating systems today have this feature, UNIX has a /tmp directory in memory, and z/OS uses VIO storage pools.
This is important, as memory would be made to look like disk externally, as "cache", in the 1990s.
IBM AIX v3 introduces Logical Volume Manager (LVM). LVM maps the LUNs from external RAID controllers into virtual disks inside the UNIX server. The mapping can combine the capacity of multiple physical LUNs into a large internal volume. This was all done by software within the server, completely independent of the storage vendor, so again no lock-in.
IBM introduces the Virtual Tape Server (VTS). This was a disk array that emulated a tape library. A mapping of virtual tapes to physical tapes was done to allow full utilization of larger and larger tape cartridges. While many people today mistakenly equate "storage virtualization" with "disk virtualization", in reality it can be implemented on other forms of storage. The disk array was referred to as the "Tape Volume Cache". By using disk, the VTS could mount an empty "scratch" tape instantaneously, since no physical tape had to be mounted for this purpose.
Contradicting its "tape is dead" mantra, EMC later developed its CLARiiON disk library that emulates a virtual tape library (VTL).
IBM introduces the SAN Volume Controller. It involves mapping virtual disks to manage disks that could be from different frames from different vendors. Like other controllers, the SVC has multiple processors and cache memory, with the intelligence to talk to servers, and is similar in functionality to the controller components you might find inside monolithic "controller+disk" configurations like the IBM DS8300, EMC Symmetrix, or HDS TagmaStore USP. SVC can map the virtual disk to physical disk one-for-one in "image mode", as HDS does, or can also map virtual disks across physical managed disks, using a similar mapping table, to provide advantages like performance improvement through striping. You can take any virtual disk out of the SVC system simply by migrating it back to "image mode" and disconnecting the LUN from management. Again, no vendor lock-in.
The HDS USP and NSC can run as regular disk systems without virtualization, or the virtualization can be enabled to allow external disks from other vendors. HDS usually counts all USP and NSC sold, but never mention what percentage these have external disks attached in virtualization mode. Either they don't track this, or too embarrassed to publish the number. (My guess: single digit percentage).
Few people remember that IBM also introduced virtualization in both controller+disk and SAN switch form factors. The controller+disk version was called "SAN Integration Server", but people didn't like the "vendor lock-in" having to buy the internal disk from IBM. They preferred having it all external disk, with plenty of vendor choices. This is perhaps why Hitachi now offers a disk-less version of the NSC 55, in an attempt to be more like IBM's SVC.
IBM also had introduced the IBM SVC for Cisco 9000 blade. Our clients didn't want to upgrade their SAN switch networking gear just to get the benefits of disk virtualization. Perhaps this is the same reason EMC has done so poorly with its "Invista" offering.
So, bottom line, storage virtualization can, and has, been delivered in the operating system software, in the server's host bus adapter, inside SAN switches, and in storage controllers. It can be delivered anywhere in the path between application and physical media. Today, the two major vendors that provide disk virtualization "in the storage controller" are IBM and HDS, and the three major vendors that provide tape virtualization "in the storage controller" are IBM, Sun/STK, and EMC. All of these involve a mapping of logical to physical resources. Hitachi uses a one-for-one mapping, whereas IBM additionally offers more sophisticated mappings as well.
The keynote was led by Phil Tasker, IBM Business Unit Executive (BUE) for STG Education Programs in Growth Markets, then Joe Screnci, head of IBM Storage Sales for Australia. IBM is in the Top 10 Training Hall of Fame, and conducts over 40,000 classes worldwide, resulting in over 1.3 million student days of instructions. IBM Systems Lab and Training technical hosts over three dozen conferences like this one every year.
Next was Clod Barrera, Distinguished Engineer and Chief Technical Strategist for the IBM System Storage product line. He covered future trends in storage as they relate to IBM's Smarter COmputing initiative.
Storage for the Clouds
Clod Barrera presented this break-out session on Cloud Storage. He covered why clouds matter, the various types and purposes of cloud, technology and architectures, and where IBM is headed to support this trend.
Storage for Cloud computing was $1 Billion USD business in 2010, and is expected to grow 32 percent CAGR through, compared to 3.8 percent for non-cloud storage. Clod estimates that 10 to 15 percent of all storage will be in cloud deployments by 2015. Of this storage, analysts expect 50 percent in private clouds, and the other 50 percent in public clouds. For private clouds, clients are looking to "Cloudify" their existing IT infrastructures. For public clouds, the projects are mostly green field.
IBM is also looking to the "arms dealer" of choice for Telcos and other companies looking to launch their own Cloud Services. IBM has a Cloud Services Provider Platform (CSP2) specifically to provide all the tools and technologies needed to make this possible.
Last month, IBM launched several new solutions for Cloud. The IBM Starter Kit for Cloud will help existing IT environments adopt cloud technologies. The IBM Service Agility Accelerator for Cloud is available for more advanced deployments. IBM Service Delivery Manager (ISDM) integrates a collection of software to provide complete integrated service management. IBM CloudBurst provides an integrated hardware-and-software stack for both x86 and POWER chipsets.
Multi-tenancy is also a big issue, and this varies depending on deployment model: IaaS, PaaS, or SaaS. Multi-tenancy is needed to help divide up management tasks, and to ensure that shared resources are paid for and meet SLA requirements accordingly.
Clod feels there are good reasons to use high performance, transactional SAN storage for VMware environments, versus NAS which many people consider simpler to deploy. IBM is also active in open standards, including SNIA's Cloud Data Management Interface [CDMI].
Journey to the Private Cloud
Gary Luke from Brocade provided this session on IBM's SAN384B-2 and SAN768B-2 SAN directors. Brocade is one of IBM's suppliers for SAN switches, and thanks to TRILL being adopted last August by IETF, supports multi-hop FCoE configurations! However, Gary did not talk about FCoE, but rather native FCP and FICON support in these new directors.
According to VMware, only 30 percent of x86 workloads are virtualized by any hypervisor. Gary feels that server virtualization and the use of Solid-State Drives (SSD) in disk arrays are driving existing 8 Gbps SAN to upgrade to 16 Gbps. Gary feels that Fibre-Channel based SANs are best positioned to handle unpredictable peaks in a 24-by-7 world.
The SAN384B-2 can house up to 256 ports (8 Gbps) or 192 ports (16 Gbps) in four slots, 9U chassis. The SAN768B-2 can handle twice these, in a 12U chassis. The nice thing about the 16Gbps ports is that they can auto-negotiate down to 10, 8, 4 and 2 Gbps. This is far better than typical N-2 support, often referred to as the speeds supported, such as 4/2/1 and 8/4/2. An upcoming FOS release will allow people with previous generation SAN384B-1/SAN768B-1 directors to move their 8Gbps blades over to the new SAN384B-2/SAN768B-2 generation models.
Since most CWDM and DWDM only support maximum 10 Gbps FC and 10GbE, Brocade's 16Gbps can automatically drop down to 10 Gbps for direct attachment to CWDM/DWDM, rather than having a step-down box normally required.
A major advancement is the change from copper to optical "Inter-Chassis Links" (ICL). Unlike Inter-switch links (ISL) that use up SAN ports on each box, the ICL is faster, more efficient and does not consume ports. Normally, clients would connect two directors together, but now you can connect up to six chassis together! For example, you can have four SAN368B-2 connected to your host servers, ICL attached to two SAN768B-2, that are then connected to your disk and tape storage devices. The fiber optic ICL allow for up to 50 meters distance. Combining six chassis together would allow the complex to support over 3,000 ports (8 Gbps) or 2,300 ports (16 Gbps).
The SAN384B-2 and SAN768B-2 supports "virtual SAN" logical switches, traffic isoliation (TI) zones, fabric-assigned WWNNs, and fabric-based QoS.
Lastly, Brocade offers a free utility called [SANhealth] that will gather data from your b-type, m-type and even Cisco MDS-based SAN. The data can then be sent to Brocade for analysis, and Brocade will then email back some nice Visio graphs, spreadsheets and other analysis results on the health of your SAN.
Well, this week I am in Maryland, just outside of Washington DC. It's a bit cold here.
Robin Harris over at StorageMojo put out this Open Letter to Seagate, Hitachi GST, EMC, HP, NetApp, IBM and Sun about the results of two academic papers, one from Google, and another from Carnegie Mellon University (CMU). The papers imply that the disk drive module (DDM) manufacturers have perhaps misrepresented their reliability estimates, and asks major vendors to respond. So far, NetAppand EMC have responded.
I will not bother to re-iterate or repeat what others have said already, but make just a few points. Robin, you are free to consider this "my" official response if you like to post it on your blog, or point to mine, whatever is easier for you. Given that IBM no longer manufacturers the DDMs we use inside our disk systems, there may not be any reason for a more formal response.
Coke and Pepsi buy sugar, Nutrasweet and Splenda from the same sources
Somehow, this doesn't surprise anyone. Coke and Pepsi don't own their own sugar cane fields, and even their bottlers are separate companies. Their job is to assemble the components using super-secret recipes to make something that tastes good.
IBM, EMC and NetApp don't make DDMs that are mentioned in either academic study. Different IBM storage systems uses one or more of the following DDM suppliers:
Seagate (including Maxstor they acquired)
Hitachi Global Storage Technologies, HGST (former IBM division sold off to Hitachi)
In the past, corporations like IBM was very "vertically-integrated", making every component of every system delivered.IBM was the first to bring disk systems to market, and led the major enhancements that exist in nearly all disk drives manufactured today. Today, however, our value-add is to take standard components, and use our super-secret recipe to make something that provides unique value to the marketplace. Not surprisingly, EMC, HP, Sun and NetApp also don't make their own DDMs. Hitachi is perhaps the last major disk systems vendor that also has a DDM manufacturing division.
So, my point is that disk systems are the next layer up. Everyone knows that individual components fail. Unlike CPUs or Memory, disks actually have moving parts, so you would expect them to fail more often compared to just "chips".
If you don't feel the MTBF or AFR estimates posted by these suppliers are valid, go after them, not the disk systems vendors that use their supplies. While IBM does qualify DDM suppliers for each purpose, we are basically purchasing them from the same major vendors as all of our competitors. I suspect you won't get much more than the responses you posted from Seagate and HGST.
American car owners replace their cars every 59 months
According to a frequently cited auto market research firm, the average time before the original owner transfers their vehicle -- purchased or leased -- is currently 59 months.Both studies mention that customers have a different "definition" of failure than manufacturers, and often replace the drives before they are completely kaput. The same is true for cars. Americans give various reasons why they trade in their less-than-five-year cars for newer models. Disk technologies advance at a faster pace, so it makes sense to change drives for other business reasons, for speed and capacity improvements, lower power consumption, and so on.
The CMU study indicated that 43 percent of drives were replaced before they were completely dead.So, if General Motors estimated their cars lasted 9 years, and Toyota estimated 11 years, people still replace them sooner, for other reasons.
At IBM, we remind people that "data outlives the media". True for disk, and true for tape. Neither is "permanent storage", but rather a temporary resting point until the data is transferred to the next media. For this reason, IBM is focused on solutions and disk systems that plan for this inevitable migration process. IBM System Storage SAN Volume Controller is able to move active data from one disk system to another; IBM Tivoli Storage Manager is able to move backup copies from one tape to another; and IBM System Storage DR550 is able to move archive copies from disk and tape to newer disk and tape.
If you had only one car, then having that one and only vehicle die could be quite disrupting. However, companies that have fleet cars, like Hertz Car Rentals, don't wait for their cars to completely stop running either, they replace them well before that happens. For a large company with a large fleet of cars, regularly scheduled replacement is just part of doing business.
This brings us to the subject of RAID. No question that RAID 5 provides better reliability than having just a bunch of disks (JBOD). Certainly, three copies of data across separate disks, a variation of RAID 1, will provide even more protection, but for a price.
Robin mentions the "Auto-correlation" effect. Disk failures bunch up, so one recent failure might mean another DDM, somewhere in the environment, will probably fail soon also. For it to make a difference, it would (a) have to be a DDM in the same RAID 5 rank, and (b) have to occur during the time the first drive is being rebuilt to a spare volume.
The human body replaces skin cells every day
So there are individual DDMs, manufactured by the suppliers above; disk systems, manufactured by IBM and others, and then your entire IT infrastructure. Beyond the disk system, you probably have redundant fabrics, clustered servers and multiple data paths, because eventually hardware fails.
People might realize that the human body replaces skin cells every day. Other cells are replaced frequently, within seven days, and others less frequently, taking a year or so to be replaced. I'm over 40 years old, but most of my cells are less than 9 years old. This is possible because information, data in the form of DNA, is moved from old cells to new cells, keeping the infrastructure (my body) alive.
Our clients should approach this in a more holistic view. You will replace disks in less than 3-5 years. While tape cartridges can retain their data for 20 years, most people change their tape drives every 7-9 years, and so tape data needs to be moved from old to new cartridges. Focus on your information, not individual DDMs.
What does this mean for DDM failures. When it happens, the disk system re-routes requests to a spare disk, rebuilding the data from RAID 5 parity, giving storage admins time to replace the failed unit. During the few hours this process takes place, you are either taking a backup, or crossing your fingers.Note: for RAID5 the time to rebuild is proportional to the number of disks in the rank, so smaller ranks can be rebuilt faster than larger ranks. To make matters worse, the slower RPM speeds and higher capacities of ATA disks means that the rebuild process could take longer than smaller capacity, higher speed FC/SCSI disk.
According to the Google study, a large portion of the DDM replacements had no SMART errors to warn that it was going to happen. To protect your infrastructure, you need to make sure you have current backups of all your data. IBM TotalStorage Productivity Center can help identify all the data that is "at risk", those files that have no backup, no copy, and no current backup since the file was most recently changed. A well-run shop keeps their "at risk" files below 3 percent.
So, where does that leave us?
ATA drives are probably as reliable as FC/SCSI disk. Customers should chose which to use based on performance and workload characteristics. FC/SCSI drives are more expensive because they are designed to run at faster speeds, required by some enterprises for some workloads. IBM offers both, and has tools to help estimate which products are the best match to your requirements.
RAID 5 is just one of the many choices of trade-offs between cost and protection of data. For some data, JBOD might be enough. For other data that is more mission critical, you might choose keeping two or three copies. Data protection is more than just using RAID, you need to also consider point-in-time copies, synchronous or asynchronous disk mirroring, continuous data protection (CDP), and backup to tape media. IBM can help show you how.
Disk systems, and IT environments in general, are higher-level concepts to transcend the failures of individual components. DDM components will fail. Cache memory will fail. CPUs will fail. Choose a disk systems vendor that combines technologies in unique and innovative ways that take these possibilities into account, designed for no single point of failure, and no single point of repair.
So, Robin, from IBM's perspective, our hands are clean. Thank you for bringing this to our attention and for giving me the opportunity to highlight IBM's superiority at the systems level.