Latest SPC-2 performance results – chart of the month

Spider chart top 10 SPC-1 MB/second broken out by workload LFP, LDQ and VODIn the figure above you can see one of the charts from our latest performance dispatch on SPC-1 and SPC-2  benchmark results. The above chart shows SPC-2 throughput results sorted by aggregate MB/sec order, with all three workloads broken out for more information.

Just last quarter I was saying it didn’t appear as if any all-flash system could do well on SPC-2, throughput intensive workloads.  Well I was wrong (again) and with an aggregate MBPS™ of ~33.5GB/sec. Kaminario’s all-flash K2 took the SPC-2 MBPS results to a whole different level, almost doubling the nearest competitor in this category (Oracle ZFS ZS3-4).

Ok, Howard Marks (deepstorage.net), my GreyBeardsOnStorage podcast co-host and long-time friend, had warned me that SSDs had the throughput to be winners at SPC-2, but they would probably cost to much to be viable.  I didn’t believe him at the time — how wrong could I be.

As for cost, both Howard and I misjudged this one. The K2 came in at just under a $1M USD, whereas the #2, Oracle system was under $400K. But there were five other top 10 SPC-2 MPBS systems over $1M so the K2, all-flash system price was about average for the top 10.

Ok, if cost and high throughput aren’t the problem why haven’t we seen more all-flash systems SPC-2 benchmarks.  I tend to think that most flash systems are optimized for OLTP like update activity and not sequential throughput. The K2 is obviously one exception. But I think we need to go a little deeper into the numbers to understand just what it was doing so well.

The details

The LFP (large file processing) reported MBPS metric is the average of 1MB and 256KB data transfer sizes, streaming activity with 100% write, 100% read and 50%:50% read-write. In K2’s detailed SPC-2 report, one can see that for 100% write workload the K2 was averaging ~26GB/sec. while for the 100% read workload the K2 was averaging ~38GB/sec. and for the 50:50 read:write workload ~32GB/sec.

On the other hand the LDQ workload appears to be entirely sequential read-only but the report shows that this is made up of two workloads one using 1MB data transfers and the other using 64KB data transfers, with various numbers of streams fired up to generate  stress. The surprising item for K2’s LDQ run is that it did much better on the 64KB data streams than the 1MB data streams, an average of 41GB/sec vs. 32GB/sec.. This probably says something about an internal flash data transfer bottleneck at large data transfers someplace in the architecture.

The VOD workload also appears to be sequential, read-only and the report doesn’t indicate a data transfer size but given K2’s actual results, averaging ~31GB/sec it would seem to indicate it was on the order of 1MB.

So what we can tell is that K2’s SSD write throughput is worse than reads (~1/3rd worse) and relatively smaller sequential reads are better than relatively larger sequential reads (~1/4 better).  But I must add that even at the relatively “slower write throughput”, the K2 would still have beaten the next best disk-only storage system by ~10GB/sec.

Where’s the other all-flash SPC-2 benchmarks?

Prior to K2 there was only one other all-flash system (TMS RamSan-630) submission for SPC-2. I suspect that writing 26 GB/sec. to an all-flash system would be hazardous to its health and maybe other all-flash storage system vendors don’t want to encourage this type of activity.

Just for the record the K2 SPC-2 result has been submitted for “review” (as of 18Mar2014) and may be modified before finally “accepted”. However, the review process typically doesn’t impact performance results as much as other report items. So, officially, we will need to await for final acceptance before we can truly believe these numbers.

Comments?

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The complete SPC  performance report went out in SCI’s February 2014 newsletter.  But a copy of the report will be posted on our dispatches page sometime next quarter (if all goes well).  However, you can get the latest storage performance analysis now and subscribe to future free newsletters by just using the signup form above right.

Even more performance information and OLTP, Email and Throuphput ChampionCharts for Enterprise, Mid-range and SMB class storage systems are also available in SCI’s SAN Buying Guide, available for purchase from  website.

As always, we welcome any suggestions or comments on how to improve our SPC  performance reports or any of our other storage performance analyses.

SCI’s latest SPC-2 performance results analysis – chart-of-the-month

SCISPC110822-002 (c) 2011 Silverton Consulting, All Rights Reserved
SCISPC110822-002 (c) 2011 Silverton Consulting, All Rights Reserved

There really wasn’t that many new submissions for the Storage Performance Council SPC-1 or SPC-2 benchmarks this past quarter (just the new Fujitsu DX80S2 SPC-2 run) so we thought it time to roll out a new chart.

The chart above shows a scatter plot of the number of disk drives in a submission vs. the MB/sec attained for the Large Database Query (LDQ) component of an SPC-2 benchmark.

As one who follows this blog and our twitter feed knows we continue to have an ongoing, long running discussion on how I/O benchmarks such as this are mostly just a measure of how much hardware (disks and controllers) are thrown at them.  We added a linear regression line to the above chart to evaluate the validity of that claim and as clearly shown above, disk drive count is NOT highly correlated with SPC-2 performance.

We necessarily exclude from this analysis any system results that used NAND based caching or SSD devices so as to focus specifically on disk drive count relevance.   There are not a lot of these in SPC-2 results but there are enough to make this look even worse.

We chose to only display the LDQ segment of the SPC-2 benchmark because it has the best correlation or highest R**2 at 0.41 between workload and disk count. The aggregate MBPS as well as the other components of the SPC-2 benchmark include video on demand (VOD) and large file processing (LFP) both of which had R**2’s of less than 0.36.

For instance, just look at the vertical centered around 775 disk drives.  There are two systems that show up here, one doing ~ 6000 MBPS and the other doing ~11,500 MBPS – quite a difference.  The fact that these are two different storage architectures from the same vendor is even more informative??

Why is the overall correlation so poor?

One can only speculate but there must be something about system sophistication at work in SPC-2 results.  It’s probably tied to better caching, better data layout on disk, and better IO latency but it’s only an educated guess.  For example,

  • Most of the SPC-2 workload is sequential in nature.  How a storage system detects sequentiality in a seemingly random IO mix is an art form and what a system does armed with that knowledge is probably more of a science.
  • In the old days of big, expensive CKD DASD, sequential data was all laid out in consecutively (barring lacing) around a track and up a cylinder.  These days of zoned FBA disks one can only hope that sequential data resides in laced sectors, along consecutive tracks on the media, minimizing any head seek activity.  Another approach,  popular this last decade, has been to throw more disks at the problem, resulting in many more seeking heads to handle the workload and who care where the data lies.
  • IO latency is another factor.  We have discussed this before (see Storage throughput vs IO response time and why it matters. But one key to systems throughput is how quickly data gets out of cache and into the hands of servers. Of course the other part to this, is how fast does the storage system get the data from sitting on disk into cache.

Systems that do these better will perform better on SPC-2 like benchmarks that focus on raw sequential throughput.

Comments?

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The full SPC performance report went out to our newsletter subscribers last month.  A copy of the full report will be up on the dispatches page of our website later next month. However, you can get this information now and subscribe to future newsletters to receive these reports even earlier by just sending us an email or using the signup form above right.

As always, we welcome any suggestions on how to improve our analysis of SPC results or any of our other storage system performance discussions.