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Jumbo Frames for NFS & iSCSI VMWare Datastores

We have been working on a comparison between VMware datastores running on NFS, iSCSI, and FC. (Stay tuned. We will publish those results shortly.) Along the way we were reminded of the performance boost that jumbo frames can provide. These tests were run using the same 'boot storm' test harness on the server side we have used before (details can be found at the end of this post). The question is, "How much faster will ESX be with jumbo frames enabled?"

Let's jump right to the answer...

  No Jumbo Frames (M:SS) Jumbo Frames Enabled (M:SS)
% Improvement
NFS 5:10 4:25 14.5%
iSCSI 4:12 3:48 9.5%

In this test, enabling jumbo frames improves iSCSI performance by nearly 10% and NFS performance by almost 15%. Improving performance by 10-15% is a significant win when there is no cost required to do it. The simple change of enabling jumbo frames on the ESX servers, the network switch, and the storage array made the existing infrastructure faster. Much like block alignment, there is no downside.

Infrastructure details: The test infrastructure consists of 4 dual socket Intel Nehalem-EP servers with 48GB of RAM each. Each server is connected to a 10GbE switch. A FAS3170 is connected to the same 10GbE switch with a single 10GbE link. There are 200 virtual machines: 50 Microsoft Windows 2003, 50 Microsoft Vista, 50 Microsoft Windows 2008, and 50 linux. Each operating system type is installed in a separate NetApp FlexVol for a total of 4 volumes. The guests were separated into multiple datastores to allow the VMware ESX systems to use 4 different NFS mount points on each ESX system. Each physical server mounts all 4 NFS datastores and the guests were split evenly across the 4 physical servers. The timing listed in the table is the time from the start of the 200 systems booting until the time the last system acquired an IP address.

Originally posted at http://ctistrategy.com

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