Since our last blog post on this subject there have been 6 new entries in LRT Top 10 (#3-6 &, 9-10). As can be seen here which combines SPC-1 and 1/E results, response times vary considerably. 7 of these top 10 LRT results come from subsystems which either have all SSDs (#1-4, 7 & 9) or have a large NAND cache (#5). The newest members on this chart were the NetApp 3270A and the Xiotech Emprise 5000-300GB disk drives which were published recently.
The NetApp FAS3270A, a mid-range subsystem with 1TB of NAND cache (512MB in each controller) seemed to do pretty well here with all SSD systems doing better than it and a pair of all SSD systems doing worse than it. Coming in under 1msec LRT is no small feat. We are certain the NAND cache helped NetApp achieve their superior responsiveness.
What the Xiotech Emprise 5000-300GB storage subsystem is doing here is another question. They have always done well on an IOPs/drive basis (see SPC-1&-1/E results IOPs/Drive – chart of the month) but being top ten in LRT had not been their forte, previously. How one coaxes a 1.47 msec LRT out of a 20 drive system that costs only ~$41K, 12X lower than the median price(~$509K) of the other subsystems here is a mystery. Of course, they were using RAID 1 but so were half of the subsystems on this chart.
The full performance dispatch will be up on our website in a couple of weeks but if you are interested in seeing it sooner just sign up for our free monthly newsletter (see upper right) or subscribe by email and we will send you the current issue with download instructions for this and other reports.
As always, we welcome any constructive suggestions on how to improve our storage performance analysis.
Not a lot of Storage Performance Council (SPC) benchmark submissions this past quarter just a new SPC-1/E from HP StorageWorks on their 6400 EVA with SSDs and a new SPC-1 run for Oracle Sun StorageTek 6780. Recall that SPC-1/E executes all the same tests as SPC-1 but adds more testing with power monitoring equipment attached to measure power consumption at a number of performance levels.
With this chart we take another look at the storage energy consumption (see my previous discussion on SSD vs. drive energy use). As shown above we graph the IOPS/watt for three different performance environments: Nominal, Medium, and High as defined by SPC. These are contrived storage usage workloads to measure the varibility in power consumed by a subsystem. SPC defines the workloads as follows:
Nominal usage is 16 hours of idle time and 8 hours of moderate activity
Medium usage is 6 hours of idle time, 14 hours of moderate activity, and 4 hours of heavy activity
High usage is 0 hours of idle time, 6 hours of moderate activity and 18 hours of heavy activity
As for activity, SPC defines moderate activity at 50% of the subsystem’s maximum SPC-1 reported performance and heavy activity is at 80% of its maximum performance.
With that behind us, now on to the chart. The HP 6400 EVA had 8-73GB SSD drives for storage while the two Xiotech submissions had 146GB/15Krpm and 600GB/15Krpm drives with no flash. As expected the HP SSD subsystem delivered considerably more IOPS/watt at the high usage workload – ~2X the Xiotech with 600GB drives and ~2.3X the Xiotech with 146GB drives. The multipliers were slightly less for moderate usage but still substantial nonetheless.
SSD nominal usage power consumption
However, the nominal usage bears some explanation. Here both Xiotech subsystems beat out the HP EVA SSD subsystem at nominal usage with the 600GB drive Xiotech box supporting ~1.3X the IOPS/watt of the HP SSD system. How can this be? SSD idle power consumption is the culprit.
The HP EVA SSD subsystem consumed ~463.1W at idle while the Xiotech 600GB only consumed ~23.5W and the Xiotech 146GM drive subsystem consumed ~23.4w. I would guess that the drives and perhaps the Xiotech subsystem have considerable power savings algorithms that shed power when idle. For whatever reason the SSDs and HP EVA don’t seem to have anything like this. So nominal usage with 16Hrs of idle time penalizes the HP EVA SSD system resulting in the poors IOPS/watt for nominal usage shown above..
Rays reading: SSDs are not meant to be idled alot and disk drives, especially the ones that Xiotech are using have very sophisticated power management that maybe SSDs and/or HP should take a look at adopting.
The full SPC performance report will go up on SCI’s website next month in our dispatches directory. However, if you are interested in receiving this sooner, just subscribe by email to our free newsletter and we will send you the current issue with download instructions for this and other reports.
As always, we welcome any suggestions on how to improve our analysis of SPC performance information so please comment here or drop us a line.