Which way the wind blows: Flash Memory in the Data Center

First let’s just take a quick look backwards to see what was considered state of the art a year ago. A company called STEC was making Flash-based hard drives and selling them to big players in the enterprise storage market like IBM and NetApp. I depends solely on The Register for this information as you can read here: STEC becalmed as Fusion-io streaks ahead

STEC flooded the market according to The Register and subsequently the people using their product were suddenly left with a glut of product using these Fibre Channel based Flash Drives (Solid State Disk Drives – SSD). And the gains in storage array performance followed. However the supply exceeded the demand and EMC is stuck with a raft of last year’s product that it hasn’t marked up and re-sold to its current customers. Which created an opening for a similar but sexier product Fusion-io and it’s PCIe based Flash hard drive. Why sexy?

The necessity of a Fibre Channel interface for the Enterprise Storage market has long been an accepted performance standard. You need at minimum the theoretical 6GB/sec of FC interfaces to compete. But for those in the middle levels of the Enterprise who don’t own the heavy iron of giant multi-terabyte storage arrays, there was/is now an entry point through the magic of the PCIe 2.0 interface. Any given PC whether a server or not will have open PCIe slots in which a

Fusion-io SSD card could be installed. That lower threshold (though not a lower price necessarily) has made Fusion-io the new darling for anyone wanting to add SSD throughput to their servers and storage systems. And now everyone wants Fusion-io not the re-branded STEC Fibre Channel SSDs everyone was buying a year ago.

Anyone who has studied history knows in the chain of human relations there’s always another competitor out there that wants to sit on your head. Enter LSI and Seagate with a new product for the wealthy, well-heeled purchasing agent at your local data center: LSI and Seagate take on Fusion-io with flash

Rather than create a better/smarter Fibre Channel SSD, LSI and Seagate are assembling a card that plugs into PCIe slot of a storage array or server to act as a high speed cache to the slower spinning disks. The Register refers to three form factors in the market now RamSan, STEC and Fusion-io. Because Fusion-io seems to have moved into the market at the right time and is selling like hot cakes, LSI/Seagate are targeting that particular form factor with it’s SSS6200.

STEC is also going to create a product with a PCIe interface and Micron is going to design a product too. LSI’s product will not be available to ship until the end of the year.  In terms of performance the speeds being target are comparable between the Fusion-io Duo and the LSI SSS6200 (both using single level cell memory). So let the price war begin! Once we finally get some competition in the market I would hope the entry level price of Fusion-io (~$35,000) finally erodes a bit. It is a premium product right now intended to help some folks do some heavy lifting.

My hope for the future is we could see something comparable (though much less expensive and scaled down) available on desktop machines. I don’t care if it’s built-in to a spinning SATA hard drive (say as a high speed but very large cache) or some kind of card plugging into a bus on the motherboard (like the failed Intel Speed Boost cache). If a high speed flash cache could become part of the standard desktop PC architecture to sit in front of monstrous single hard drives (2TB or higher nowadays) we might get faster response from our OS of choice, and possible better optimization of reads/writes to fairly fast but incredibly dense and possibly more error prone HDDs. I say this after reading about the big charge by Western Digital to move from smaller blocks of data to the 4K block.

Much wailing and gnashing of teeth has accompanied the move recently by WD to address the issue of error correcting Cycle Redundancy Check (CRC) algorithms on the hard drives. Because 2Terabyte drives have so many 512bit blocks more and more time and space is taken up doing the CRC check as data is read and written to the drive. A larger block made up of 4096 bits instead of 512 makes the whole thing 4x less wasteful and possibly more reliable even if some space is wasted to small text files or web pages. I understand completely the implication and even more so, old-timers like Steve Gibson at GRC.com understand the danger of ever larger single hard drives. The potential for catastrophic loss of data as more data blocks need to be audited can numerically become overwhelming to even the fastest CPU and SATA bus. I think I remember Steve Gibson expressing doubts as to how large hard drives could theoretically become.

As the creator of the SpinRite data recovery utility he knows fundamentally the limits to the design of the Parallel ATA interface. Despite advances in speeds, error-correcting hasn’t changed and neither has the quality of the magnetic medium used on the spinning disks. One thing that has changed is the physical size of the blocks of data. They have gotten infinitesimally smaller with each larger size of disk storage. The smaller the block of data the more error correcting must be done. The more error-correcting the more space to write the error-correcting information. Gibson himself observers something as random as cosmic rays can flip bits within a block of data at those incredibly small scales of the block of data on a 2TByte disk.

So my hope for the future is a new look at the current state of the art motherboard, chipset, I/O bus architecture. Let’s find a middle level, safe area to store the data we’re working on, one that doesn’t spontaneously degrade or is too susceptible to random errors (ie cosmic rays). Let the Flash Cache’s flow, let’s get better throughput and let’s put disks into the class of reliable but slower backing stores for our SSDs.