the storage anarchist

3.021: spec sfs wars

I won't be the first to observe that most benchmarks are unrelated to anything anyone would see in the real world – no matter how hard we try, it borders on impossible to build truly representative artificial workloads. And even if we could, the second order challenge with benchmarking in the IT world is that the desire to win leads us all to often to create test configurations that would never exist in the real world.

Yet it is a dominant gene of some sort that drives us carbon-based life forms to use such artificial comparisons as the basis of what we hope are informed decisions.

The latest two entries in the SPECsfs benchmark comparisons, both of which were released within the past 24 hours or so, provide an interesting comparison of performance. In this machine-vs-machine battle, we have IBM's SONAS pitted against EMC's new VNX platform, each boasting to have shattered the SPECsfs benchmark performance records.

Now, so far as I am aware, nobody runs SPECsfs as a production workload, so the direct meaning of these results is debatable. All they really tell us is which system configuration is better at running this specific benchmark – I personally would not want to extract anything more than that from the results.

But if you look closely at the results, there is perhaps another story…

3.020: reality check - vsp vaai support

I've seen lots of bluster lately from the Hitachi PR machine about VSP being the first virtualization platform to support VMware's vStorage API for Array Integration (VAAI).

When you're next to last delivering something, I guess you gotta try something (I note that IBM has yet to deliver VAAI on either DS8K or on XIV – not surprising, since both seem to be on life support, if for different reasons).

Hitachi have spared no blather in their messaging. If you were to believe their PR proclamations, you would expect to gain all the benefits of VAAI without waiting for your existing storage platform to be upgraded with VAAI support. Just tuck it behind a spanking new VSP and forget all your troubles, they seem to say.

Reality Check time.

As Stephen Foskett essentially explains in his post VMware VAAI Storage Array Support in Plain English, VAAI was developed by VMware in cooperation of industry storage suppliers to address TWO issues:

1. Copy and Erase operations place a huge load on the servers, network and storage arrays
2. The SCSI reservation locking mechanism does not scale efficiently for large LUNs nor for large number of hosts sharing the same LUN(s)

What the Hitachi PR machine fails to mention is that moving the Bulk Zero and Bulk Copy workloads off of the server CPU is not the only benefit of a good VAAI implementation. In fact, with Done Right implementations like VMAX, moving these operations into the array allows the array to optimize the operations to further reduce the overhead and impact.