ISE: Building-Block Storage

Why a new technology -- Intelligent Storage Element -- has our storage analyst raving

As we go to press, Xiotech will be unveiling the fruits of five years' labor by Seagate's Advanced Storage Architecture Group, acquired by the Eden Prarie, MN-based storage vendor last year. The technology is called ISE, for Intelligent Storage Element. From where I'm sitting, it is potentially the most disruptive introduction in the storage world since the hard disk.

ISE is, for lack of a non-trademarked metaphor, a Lego building block for storage. Think of it as a compact brick of disk drives arranged into two sets, called datapacs. The brick comprises either ten 3.5-inch drives or 20 2.5-inch drives of any type, which are configured in a grid that leverages 75 hardware and software patents, including a high-performance RAID algorithm combined with disc firmware changes for data protection.

Each datapac in the ISE presents a gas-gauge-like monitor showing you how much performance is being used and how much capacity remains. It also tells you when drives fail -- as they inevitably will -- so you know when to replace the ISE itself. (The original version I saw in Seagate's labs had such a gauge on the outside of the box -- very retro and 1950s sci-fi-movie cool; but I'm told this feature is now going inboard'. By the time you see it, ISE will present its information via software.) When you need to replace datapacs, simple algorithms and procedures are available to migrate data to the new one, assuming the system has not performed this operation within a grid of datapacs already deployed in the rack.

Chances are good, however, that you won't be replacing datapacs very often -- certainly not as often as you replace disk drives today. 'ISE does things behind the scenes that have already demonstrated an ability to reduce the frequency of failure and replacement well below rates seen in a conventional disk subsystem. This also eliminates that nagging 'No Trouble Found' problem that is the bane of storage administrators everywhere (see below) requiring the replacement of disks that haven't actually failed but are reported to have failed by the storage subsystem.

The process begins with a completely new way to write and recover smaller increments of data on the spindles themselves. This innovation makes data recovery, even on larger drives, a much less time-consuming process. It also sets the stage for the integration of multiple drives into a single grid entity that adds performance and robustness to each datapac, and beyond that, to arrays of datapacs.

Now add on-board disk remanufacturing. You read this correctly: drive remanufacturing on the device itself. Steve Sicola (he ran ASA and is now CTO at Xiotech), Richard and Ellen Lary (Ellen is now a vice-president at Xiotech), and the other 100 or so engineers involved in the project have replicated Seagate's own processes for drive telemetry monitoring and error detection -- and drive re-manufacturing -- in firmware on the Linux-based ISE. ISE automatically performs preventive and remedial processes. It can reset disks, power cycle disks, implement head-sparing operations, recalibrate and optimize servos and heads, perform reformats on operating drives, and rewrite entire media surfaces if needed. Everything that Seagate would do if you returned a drive for service.

The result is a product that over the past 15 months of continuous operation (208 ISEs running 5900 spindles) has presented zero service events (outages caused by drive failures). A comparable storage array or SAN with traditional technology would have incurred no less than 122 media-related service events in the same timeframe.

It should be noted that the preponderance of disks returned to the factory with suspected failure conditions are determined to be "NTF" (no trouble found) when examined by the drive vendor technicians. Xiotech's ISE addresses this with a combination of preventive monitoring, self-healing, and fail-in-place architecture that is the best I've ever seen. Ever.

Another of the product's key innovations is the elimination of so-called "silent data corruption" -- which refers to data errors introduced on write. The ISE is the first to implement a new SCSI standard from ANSI T10 called DIF. Errors are corrected at write, so data can be read correctly. Eight bytes of additional data are written to disk creating a 520 byte block versus a 512 byte block to facilitate the creation, storage, and use of additional CRC protection and logical block application and logical block reference meta tagging -- critical for ensuring proper writes to virtual LUNs and blocks within virtual LUNs.

By combining a state-of-the-art data protection story with state-of-the-art performance, ISE delivers 30 percent more IOs per second than off-the-shelf drives from any disk vendor. It is certainly faster than conventional array products available today. This performance scales as the system scales: the more datapacs you add, the more performance you see courtesy of an innovative striping method that introduces little to no overhead. This is confirmed by soon–to-be-released Storage Performance Council test results that give "best in class" kudos to ISE in both SPC-1 and SPC-2 testing regimens.

In addition, let's not forget Xiotech's all-important contribution to ISE, which comes in the form of a Web-services-based ICON management platform. (We wrote about ICON and Xiotech's Web-services-based storage management approach in previous columns.) With ICON, ISE becomes a truly remarkable storage building block: fully manageable and with unbeatable reliability, scalability, and performance metrics.

I'm not sure what Xiotech is planning to charge for ISE. I do know that manufacturing costs for the box without drives was low when I last checked. Xiotech could mark it up 500 percent and not approach the purchase price of most "SAN in a Box" products coming from name brand vendors. For now, I am told that unofficial SPC calculations for the $20,820 configuration used in tests result in $3.53 per SPC-1 IOP and $32.25/MB/Sec for SPC-2. Barring anything unforeseen, spokespersons from Xiotech say that they believe ISE will offer the best value (lowest cost-per-performance metrics) of any array technology on the market. In addition to a "very competitive" acquisition price, they add, cost of ownership will be far below the costs to administer, maintain, and repair other types of arrays. If the price remains reasonable, this could be the product that makes Xiotech a household name: they will have created a key component of an enterprise storage architecture previously called a SAN before the Fibre Channel Industry Association corrupted our definition of what a SAN was supposed to be.

I think Sicola and the Larys appreciate this, having been at Digital Equipment Corporation, then Compaq, while the SAN concept was originally being conceived and articulated. ISE is the first step in fulfilling the SAN vision.

Interestingly, Seagate sold this business to Xiotech rather than launching ISE itself. I think I know why, but I'm only speculating. During my last visit to ASA at Seagate, I asked some senior managers why they were waiting to see whether their OEM customers (most of the major array companies) would embrace ISE and cut holes in their monolithic RAID arrays to accommodate these "superdrive" datapacs. Why not just sell them directly?

One person's response nearly knocked me off my chair: "Do you think that Seagate would have credibility as an array provider?" My response was that Seagate is synonymous in many minds with disk storage! Heck, if they would give me the rights to sell ISE via the Internet, as a building block storage component for designing customized purpose-built storage solutions based on application requirements, my micro-factory would savage the market share of all current storage array makers and I would be a very wealthy man.

I glanced at Sicola, who was in the room for the interview, and he was trying hard to contain his laughter. This was apparently why I had been invited, together with the notables in the analyst community, to the dog and pony show event: to help Seagate management appreciate the disruptive nature of ISE. At the end of the day, however, I believe that they perceived correctly that selling ISE directly to the consumer would put them in direct competition with their traditional OEM customers. So, they sold it to Xiotech.

In my opinion, that move underscores the real value of ISE. Above and beyond the technical bells and whistles, ISE breaks the one-size-fits-most model used by vendors to sell storage systems today. As with Lego bricks, you can use ISE to purpose-build storage. While the initial bricks will contain FC drives and an FC interface, there is no reason why you could not see subsequent models with SATA or SAS drives, or even Solid State Disc components, or units with UDP, iSCSI, iWARP, or Infiniband interconnects.

ISE is important and brilliantly disruptive. It will be interesting to see how Xiotech brings it to market and whether they have the vision to move beyond the proprietary chassis-based product and into the much larger world of true SANs. I encourage every reader to get their hands on ISE and kick the tires. Your comments are welcome:<.>

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