multiple paths on BOOT from SAN disk

Question

I am configuring a Windows OS installation to 'Boot from SAN'. I have successfully installed the windows OS. I am not certain how the multuple paths should function in this Boot From San configuration. My Clariion is a cx3-10c. My Windows 2003 server has 2 qlogic fibre cards so i have a potential of 4 paths to the Boot from SAN disk. I have used ctrl-Q to enter the BIOS of each fibre card and i have configured each card to have 2 bootable devices. The 2 bootable devices are the same lun but from each controller. I have a few questions regarding this type of configuration. How does the Server now determine which device path to use each time it boots? Will it always be the device path that i choose when i installed the windows OS? What happens if one device path goes down - if the OS is powered up will it stay up by using one of the 3 other paths automatically? What happens if one device path goes down - will one of the other 3 paths be used automatically if i restart the server? Should powerpath be installed and used to manage the multiple device paths to the OS when the OS is running? Thanks for any clarifiication received on these questions.

kelleg · Accepted Answer

First, I would suggest review the Host Connectivity Guide for Windows - there is a section specifically for setting up Boot-from-SAN.

Home > Support > Technical Documentation and Advisories > Host Connectivity/HBAs > Installation/Configuration.

If I remember, when you setup the HBA's for boot, you pick one path from one of the HBA's - remember that the boot LUN on the array will be owned by one SP and the path needs to see the LUN on the path that goes to that SP - so if you have two HBA's zoned with paths to both SPA and SPB and the boot LUN is owned by SPA, the paths to SPA are the boot paths. This occurs before the OS is involved - no Powerpath.

Once the OS is booted then PowerPath takes over the management of the paths.

glen

RRR · Answer

The boot order or controller order (whatever it is called) in the BIOS of the server determines from what HBA the system boots. If 1 of the 2 paths fails for that boot controller, the 2nd path will automatically be the active one, since the boot HBA is still working. If that HBA fails, the 2nd HBA should be the boot controller and the 2 paths from that HBA will be the working ones, the one to the SP that owns the LUN will be the primary path.

PPath will work as soon as the OS is up.

CLARiiON

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