It's official: SSDs rule the high end

Recent SPC-1 tests of Texas Memory Systems SSDs suggest that, soon enough, we'll think about spinning disks the same way we think about tape today

Last week, Texas Memory Systems published preliminary SPC-1 test results for its latest SSD-based SAN, the RamSan-630. In so doing, it firmly signaled the beginning of the end for spinning disk in performance-hungry high-end transactional storage applications. It's also made strides toward closing the cost-per-gigabyte gap between traditional disk and solid-state drives.

It should come as no surprise to anyone familiar with the performance characteristics of flash storage that an SSD SAN can handily beat a far larger and more expensive non-flash SAN. The interesting thing is to see exactly how well and how inexpensively it can do the job.

In TMS's case, it presented test results that saw a single RamSan-630 kick out 400,503 SPC-1 IOPS at a total as-tested list price of $419,292. That works out to an incredibly cheap $1.05 per SPC-1 IOPS.

It also easily outperforms the previous SPC-1 record holder -- a combination of two disk-based IBM DS8700s running behind a six-node IBM SVC (SAN Volume Controller) cluster. That test saw the overall system kick out 380,489 SPC-1 IOPS at a heart-stopping street price of over $7 million. In the end, the cost per SPC-1 IOPS worked out to $18.83 -- nearly 18 times as expensive as TMS's flash-based entry.

To be sure, there are a few enormous problems with drawing a direct comparison between a single 3U flash-based array and a hyper-redundant SAN virtualization platform that includes a small data center's worth of hardware. It's nowhere near an apples-to-apples comparison in terms of overall capabilities or redundancy.

I'm not trying to say that TMS's RamSan-630 is necessarily a better choice than the IBM SVC entry -- they are two completely different animals that fulfill drastically different sets of requirements. The tests were also submitted more than a year apart, with the IBM entry issued in February 2010. However, if you narrow your comparison to flash and traditional disk, it can tell you a few important things about the future of enterprise storage.

The TMS RamSan-630 utilizes 20 proprietary 640GB SLC flash boards instead of off-the-shelf SSDs built into a standard disk form factor. That works out to a total of approximately 12.5TB of raw capacity or a bit less than 10TB of usable space once you lose some capacity to RAID5 redundancy, wear leveling, and designate one flash board as a hot spare. On the rear end, you have a choice between up to five dual-port 8Gbps FC or 40Gbps QDR Infiniband cards for host/fabric connectivity.

To end up in second place, the IBM configuration needed to leverage a six-node SAN virtualization implementation and two entirely independent SAN fabrics with more than 2,000 spinning disks between them. The raw disk capacity of both SANs together was a gargantuan 292TB. However, all that hardware was necessary to yield a result surpassed by just a single 3RU device drawing 500w of power.

The SPC-1 testing regimen is specifically constructed to test the transactional performance of storage versus a typical OLTP (Online Transaction Proccessing) workload, so it generally doesn't take overall capacity into account. However, one interesting takeaway of these results is that the RamSan was also able to post a better cost per usable capacity at the same time it outstripped the raw performance of the significantly larger IBM solution. The IBM configuration as it was tested worked out to about $68.91 per usable gigabyte versus about $51.66 per usable gigabyte for the TMS configuration.

Both costs are an order of magnitude higher than a traditional disk configuration built for bulk capacity rather than raw transactional performance. SSDs still aren't a good fit for bulk storage applications and won't be for quite some time. However, it has been relatively unusual to see a high-performance SSD configuration beat a similarly high-performance disk configuration on a cost-per-gigabyte basis. That has been one area where disk has managed to maintain a clear lead -- but no longer.

In the high-performance storage market, disk has seen its day come and go. If history is any guide, what is true for the high-performance enterprise market now will be true for the middle and low-end market as production costs fall and large enterprise features trickle down. The day when the only thing that traditional disk will have to offer is cheap bulk storage is almost upon us.

This article, "It's official: SSDs rule the high end," originally appeared at InfoWorld.com. Read more of Matt Prigge's Information Overload blog and follow the latest developments in storage at InfoWorld.com. For the latest business technology news, follow InfoWorld.com on Twitter.

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