Improving VCB over iSCSI using Jumbo Frames?


I'm looking at ways to improve our VMware VCB backup performance - by enabling Jumbo Frames between the EqualLogic iSCSI array and the Windows Server 2003 R2 VCB proxy server - but not to the ESX 3.5 hosts, as VMware doesn't yet support Jumbo Frames for iSCSI.

By default, the MTU size on the EqualLogic uplinks is 9000 (default), however at all other points, the MTU size is the default 1500 (i.e. the Cisco 3130G ports; the ESX Hosts' iSCSI NICs; and the VCB Proxy iSCSI NICs)

A couple of questions:

  1. On a Cisco 3130G (blade switch) is it possible to set Jumbo Frames on individual switch ports? i.e. 1500 for ESX and 9000 for the EQL and VCB Proxy, but not the ESX Hosts

  2. As packet sizes will be resized, where is the most efficient place to do this?

    • Does the EQL detect that the Cisco 3130G switch port MTU is only 1500, and so resize it as it leaves the array

    • Or would the Cisco 3130 have to resize the packet from 9000 to 1500 when it receives it from the array?

  3. Lastly, what are your thoughts on using Jumbo Frames for VCB iSCSI, but not ESX iSCSI traffic; would you recommend it, and would VMware support it?

In the current environment, I'm seeing speeds of up to 100,000,000 Bytes/sec when performing a Full VM backup using the VCB framework from the command line, with most of the traffic going accross one of the two NICs dedicated to iSCSI

Software Revisions:

  • vCenter 2.5u4 (Dell M605 AMD Blade)

  • ESX3.5u4 (Dell M605 AMD Blade)

  • VCB 1.5 102898 (Dell M605 AMD Blade)

  • EqualLogic PS5000 series running firmware 4.0.5

  • Cisco 3130G (Dedicated iSCSI switches)

VCB Proxy

  • Dell M605 Blade

  • WS2K3 wSP2 with 2xquad-core 2.3GHz AMD & 4GB RAM

  • 2 x iSCSI NICS: Broadcom M5708t with Hardware and Software Flow Control Enabled (Rx & Tx)

  • EqualLogic Host Integration Toolkit v3.2.0 installed (with MPIO and Microsoft iSCSI Initiator v2.08)

  • MPIO Load Balancing Policy default at Least Queue Depth (which appears faster than Round Robin)

Lots of information I know, but I welcome any feedback

Thanks very much

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Equallogic can adapt packet size automatically.

So you can simple set all your switches port with MTU 9000 without problems.

Be sure on VCB to use last Ethernet driver, and if possible install Equallogic HIT (the last version from support site).


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Andre | | | @Andrea_Mauro
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