At VMworld 2012 we demonstrated a single eight-way VM running on vSphere 5.1 exceeding one million IOPS.  This testing illustrated the high end IOPS performance of vSphere 5.1.

In a new series of tests we have completed some additional characterization of high I/O performance using a very similar environment. The only difference between the 1 million IOPS test environment and the one used for these tests is that the number of Violin Memory Arrays was reduced from two to one (one of the arrays was a short term loan).

Hypervisor: vSphere 5.1
Server: HP DL380 Gen8
CPU: Two Intel Xeon E5-2690, HyperThreading disabled
Memory: 256GB
HBAs: Five QLogic QLE2562
Storage: One Violin Memory 6616 Flash Memory Array
VM: Windows Server 2008 R2, 8 vCPUs and 48GB.
Iometer Configuration: Random, 4KB I/O size with 16 workers

We continued to characterize the performance of vSphere 5.1 and the Violin array across a wider range of configurations and workload conditions.

Based on the types of questions that we often get from customers, we focused on RDM versus VMFS5 comparisons and the usage of various I/O sizes.  In the first series of experiments we compared RDM versus VMFS5 backed datastores using 100% read workload mix while ramping up the I/O size.

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As you can see from the above graph, VMFS5 yielded roughly equivalent performance to that of RDM backed datastores.  Comparing the average of the deltas across all data points showed performance within 1% of RDM for both IOPS and MB/s.  As expected, the number of IOPS decreased after we exceed the default array block size of 4KB, but the throughput continued to scale, approaching 4500 MB/s at both 8KB and 16KB sizes.

For our second series of experiments, we continued to compare RDM versus VMFS5 backed datastores through a progression of block sizes, but this time we altered the workload mix to include 60% reads and 40% writes.

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Violin Memory arrays use a 4KB sector size and perform at their optimal level when managing 4KB blocks. This is very visible in the above IOPS results at the 4KB block size. In the above graph, comparing RDM and VMFS5 IOPS, you can see that VMFS5 performs very well with a 60% read, 40% write mix.  Throughputs continued to scale in a similar fashion as the read-only experimentation and VMFS5 performance for both IOPS and MB/s were within .01% of RDM performance when comparing the average of the deltas across all data points.

The amount of I/O, with just one eight-way VM running on one Violin storage array, is both considerable and sustainable at many I/O sizes.  It’s also noteworthy to point out that running a 60% read and 40% write I/O mix still generated substantial IOPs and bandwidth. While in most cases a single VM won’t need to drive nearly this much I/O traffic, these experiments show that vSphere 5.1 is more than capable of handling it.