Network Computing is part of the Informa Tech Division of Informa PLC

This site is operated by a business or businesses owned by Informa PLC and all copyright resides with them. Informa PLC's registered office is 5 Howick Place, London SW1P 1WG. Registered in England and Wales. Number 8860726.

Optimizing iSCSI & VMware: Page 3 of 4

4) iSCSI HBAs similarly don't provide the huge performance or CPU utilization boost vendors claim, and old-line FC storage guys believed they would. They are the only way to boot the server from SAN, so if you'd rather pay $1,000 for 2 HBA ports than buy two 73 GB drives for the server, go ahead. Since VMware itself makes host servers somewhat stateless, I wouldn't worry about boot from SAN.

Note that HBAs aren't very popular and most (70 percent or more) iSCSI VMware servers use software initiators.

5) For high performance, use software initiators in the guest OS through dedicated Ethernet ports and virtual switches. This allows you to use Microsoft's excellent multipath IO and initiator that will load balance and use multiple connections/sessions to run faster than shared connections.

This also lets you manage your iSCSI storage the same way on your physical and virtual servers, including Microsoft clusters. It also lets you use array-based snapshots, which through VSS or scripts are more than crash consistent.

On the down side, you lose ESX snapshots and the things that rely on them like SRM and maybe VCB for these VMs. If were talking about database servers, including Exchange, where the backup process does log maintenance or database validation that VCB can't do, you'll want to backup through a host agent anyway.