Booting from iSCSI to a NetApp Filer

We're replacing our Exchange Server 2003 servers and are considering booting from Internet SCSI (iSCSI) to a Network Appliance NetApp filer. The new Exchange server will have about 250 mailboxes. Do you have experience booting from an iSCSI adapter in Windows Server 2003? How does it compare with booting from a Fibre Channel Storage Area Network (SAN)?

I've used only the QLogic QLA4010C adapter to boot to an iSCSI array; to my knowledge, this is the only iSCSI setup that currently supports interrupt 13 (INT 13) extensions, which are required for booting. iSCSI offers lower cost and easier implementation at the cost of slightly reduced performance.

iSCSI is currently limited to 1Gbps throughput, although some vendors (including QLogic) have pledged support for 10Gbps when such devices are available. Fibre Channel technology typically provides 2Gbps throughput in newer products and 1Gbps in some of the older SAN arrays. Many of the Fibre Channel cards are also available in dual- and sometimes quad-port configurations. The performance improvement probably won't make much difference on an Exchange 2003 server with 250 mailboxes.

Keep in mind that backups become a concern when you use a NetApp server to host LUNs instead of using it as a Network Attached Storage (NAS) appliance. You can't restore individual files from LUNs if you use Network Data Management Protocol (NDMP) for backup; you can do so only with NAS. That limitation might not be important, depending on how you want to store Exchange backups for recovery purposes and whether you use Network Appliance's SnapManager for Exchange (which I recommend).

I haven't tried connecting a tape library to a SAN array and using multiple SAN cards in a server—one attached to the library and one attached to the array—as you can with a Fibre Channel array setup. But that solution likely would work.

—Bob Chronister

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