I was at EMCworld a couple of months back and they were showing off a preview of the next version VNX storage, which was trying to achieve a million IOPS with under a millisecond latency. Then I attended NetApp’s analyst summit and the discussion at their Flash seminar was how latency was changing the landscape of data storage and how flash latencies were going to enable totally new applications.
One executive at NetApp mentioned that IOPS was never the real problem. As an example, he mentioned one large oil & gas firm that had a peak IOPS of 35K.
Also, there was some discussion at NetApp of trying to come up with a way of segmenting customer applications by latency requirements. Aside from high frequency trading applications, online payment processing and a few other high-performance database activities, there wasn’t a lot that could easily be identified/quantified today.
IO latencies have been coming down for years now. Sophisticated disk only storage systems have been lowering latencies for over a decade or more. But since the introduction of SSDs it’s been a whole new ballgame. For proof all one has to do is examine the top 10 SPC-1 LRT (least response time, measured with workloads@10% of peak activity) results.
In looking over the top 10 SPC-1 LRT benchmarks (see Figure above) one can see a general pattern. These systems mostly use SSD or flash storage except for TMS-400, TMS 320 (IBM FlashSystems) and Kaminario’s K2-D which primarily use DRAM storage and backup storage.
Hybrid disk-flash systems seem to start with an LRT of around 0.9 msec (not on the chart above). These can be found with DotHill, NetApp, and IBM.
Similarly, you almost have to get to as “slow” as 0.93 msec. before you can find any disk only storage systems. But most disk only storage comes with a latency at 1msec or more. Between 1 and 2msec. LRT we see storage from EMC, HDS, HP, Fujitsu, IBM NetApp and others.
There was a time when the storage world was convinced that to get really good response times you had to have a purpose built storage system like TMS or Kaminario or stripped down functionality like IBM’s Power 595. But it seems that the general purpose HDS HUS, IBM Storwize, and even Huawei OceanStore are all capable of providing excellent latencies with all SSD storage behind them. And all seem to do at least in the same ballpark as the purpose built, TMS RAMSAN-620 SSD storage system. These general purpose storage systems have just about every advanced feature imaginable with the exception of mainframe attach.
It seems nowadays that there is a trifurcation of latency results going on, based on underlying storage:
- DRAM only systems at 0.4 msec to ~0.1 msec.
- SSD/flash only storage at 0.7 down to 0.2msec
- Disk only storage at 0.93msec and above.
The hybrid storage systems are attempting to mix the economics of disk with the speed of flash storage and seem to be contending with all these single technology, storage solutions.
It’s a new IO latency world today. SSD only storage systems are now available from every major storage vendor and many of them are showing pretty impressive latencies. Now with fully functional storage latency below 0.5msec., what’s the next hurdle for IT.
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Image: EAB 2006 by TMWolf
