Breaking Records … Revisited
So today I found out that we’d broken a few records of our own few days ago, which was, at least from my perspective associated with surprisingly little fanfare with the associated press release coming out late last night. I’d like to say that the results speak for themselves, and to an extent they do. NetApp now holds the top two spots, and four out of the top five results on the ranking ladder. If this were the olympics most people would agree that this represents a position of PURE DOMINATION. High fives all round, and much chest beating and downing of well deserved delicious amber beverages.
So, apart from having the biggest number (which is nice), what did we prove ?
Benchmarks are interesting to me because they are the almost perfect intersection of my interests in both technical storage performance and marketing and messaging. From a technical viewpoint, a benchmark can be really useful, but it only provides a relatively small number of proof points, and extrapolating beyond those, or making generalised conclusions is rarely a good idea.
For example, when NetApp released their SPC-1 benchmarks a few years ago, it proved a number of things
1. That under heavy load which involved a large number of random writes, a NetApp arrays performance remained steady over time
2. That this could be done while taking multiple snapshots, and more importantly while deleting and retiring them while under heavy load
3. That this could be done with RAID-6 and with a greater capacity efficiency as measured by RAW vs USED than any other submission
4. That this could be done at better levels of performance than an equivalently configured commonly used “traditional array” as exemplified by EMCs CX3-40
5. That the copy on write performance of the snapshots on an EMC array sucked under heavy load (and by implication similar copy on write snapshot implementations on other vendors arrays)
That’s a pretty good list of things to prove, especially in the face of considerable unfounded misinformation being put out at the time, and which, surprisingly is still bandied about despite the independently audited proof to the contrary. Having said that, this was not a “my number is the biggest”, exercise which generally proves nothing more than how much hardware you had available in your testing lab at the time.
A few months later we published another SPC-1 result which showed that we could pretty much doubl the numbers we’d achieved in the previous generation at a lower price per IOP with what was at the time a very competetive submission.
About two years after that we published yet another SPC-1 result with the direct replacement for the controller used in the previous test (3270 vs 3170). What this test didnt do was to show how much more load could be placed on the system, what it did do was to show that we could give our customers more IOPS at a lower latency with half the number of spindles . This was the first time we’d submitted an SPC-1e result which foucussed on energy efficiency. It showed, quite dramatically how effective our FlashCache technology was under a heavy random write workload. Its interesting to compare that submission with the previous one for a number of reasons, but for the most part, this benchmark was about Flashcache effectiveness.
We did a number of other benchmarks including Spec-SFS benchmarks that also proved the remarkable effectiveness of the Flashcache technology, showing how it could make SATA drives perform as better than Fibre channel drives, or dramatically reduce the number of fibre channel drives required to service a given workload. There were a couple of other benchmarks done which I’ll grant were “hey look at how fast our shiny new boxes can run”, but for the most part, these were all done with configurations we’d reasonably expect a decent number our customers to actually buy (no all SSD configurations).
In the mean time EMC released some “Lab Queen” benchmarks, at first I thought that EMC were trying to prove just how fast their new X-blades were for processing CIFS and NFS traffic. They did this by configuring the back end storage system in such a rediculously overengineered way as to remove any possibility that they could cause a bottleneck in any way, either that or EMC’s block storage devices are way slower than most people would assume. From an engineering perspective I think they guys in Hopkington who created those X-blades did a truly excellent job, almost 125,000 IOPS per X-Blade using 6 CPU cores is genuinely impressive to me, even if all they were doing was processing NFS/CIFS calls. You see, unlike the storage processors in a FAS or Isilon array, the X-Blade, much like the Network Processor in a SONAS system, or an Oceanspace N8500 relies on a back end block processing device to handle RAID , block checksums, write cache coherency and physical data movement to and from the disks, all of which is non-trivial work. What I find particularly interesting is that in all the benchmarks I looked at for these kinds of systems, the number of back end block storage systems was usually double that of the front end, which infers to me either that the load placed on back end systems by these benchmarks is higher than the load on the front end, or more likely that the front end / back end architecture is very sensitive to any latency on the back end systems which means the back end systems get overengineered for benchmarks. My guess is after seeing the “All Flash DMX” configuration is that Celerra’s performance is very adversly affected by even slight increases in latency in the back end and that we start seeing some nasty manifestations of little law in these architectures under heavy load.
A little while later after being present at a couple of EMC presentations (one at Cisco Live, the other at a SNIA event, where EMC staff were fully aware of my presence), it became clear to me exactly why EMC did these “my number is bigger than yours” benchmarks. Ther marketing staff at corporate created a slide that compared all of the current SPC benchmarks in a way that was accurate, compelling and completely misleading all at the same time, at least as far as the VNX portion goes. Part of this goes back to the way that vendors, including I might say Netapp, use an availability group as a point of aggregation when reporting peformance numbers, this is reasonably fair as adding Active/Active or Active/Passive availability generally slows things down due to the two phase commit nature of write caching in modular storage environments. However, the configuration of the EMC VNX VG8 Gateway/EMC VNX5700 actually involves 5 separate availability groups (1xVG8 Gateway system with 4+1 redundancy, and and 4x VNX5700 with 1+1 redundancy). Presenting this as one aggregated peformance number without any valid point of aggregation smacks of downright dishonesty to me. If NetApp had done the same thing, then, using only 4 availabilty groups, we could have claimed over 760,000 IOPS by combining 4 of our existing 6240 configurations, but we didnt, because frankly doing that is in my opinion on the other side of the fine line where marketing finesse falls off the precipice into the shadowy realm of deceptive practice.
Which brings me back to my original question, what did we prove with our most recent submissions, well three things come to mind
1. That Netapp’s Ontap 8.1 Cluster mode solution is real, and it performs briliiantly
2. It scales linearly as you add nodes (more so than the leading competitors)
3. That scaling with 24 big nodes gives you better performance and better efficiency than scaling with hundreds of smaller nodes (at least for the SPEC benchmark)
This is a valid configuration using a single vserver as a point of aggregation across the cluster, and trust me, this is only the beginning.
As always, comments and criticism is welcome.