SAN redundant paths

[dani_bosch]

Hello,

When reading ESXi Boot from SAN instructions for UCS, I came across the following sentence:

"Configure a LUN or RAID volume on your SAN, then  connect to the SAN and verify that one (and only one) path exists from  the SAN HBA to the LUN".

I don't understand this sentence, as the design best practices in SAN, correct me if I'm wrong, make each path from HBA to LUN split in 2 (one for each Storage Processor).

What am I missing here?

Thanks a lot,

[Robert Burns]

Dani,

This references the installation process only.  Once the installation process has been complete you can present multiple boot paths (primary & secondary).  Best practice for any SAN installation is to present a single path during initial install.

Regards,

Robert

[dani_bosch]

Then during the installation, I have to disable the second vHBA and the second Storage Processor of the cabin, and right after the installation of the ESXi I have to reenable them again? Would the process be pretty much like it?

Thanks,

[Robert Burns]

Correct.  What some people do is use two different boot policies.  One for installation with a single path defined, and one for regular operations with all paths presented.  After the OS has been installed, which the boot policies on the Service Profile, allow the blade to re-associated the changes, and you're all set.  This practice applies to any server, rack or blade when doing SAN installations and multipathing drivers are not loaded until the full image has been installed.

Regards,

Robert

[Jeremy Waldrop]

For ESXi 4.1 you do not have to hide the redundant paths during install. I used to have to do this with ESX 4 classic and I still have to for Windows or Linux but ESXi installs fine seeing all paths.

[David McFarland]

An easy way is to disable the fc path to a vHBA path by going into the Service Profile, vHBA config and setting its VSAN to another VSAN that it is not zoned in. By default VSAN 1 is always available. But, if VSAN 1 is in use, create a new VSAN, say VSAN 42 (pick something that doesn't exist anywhere in your SAN fabric) and assign the vHBA to VSAN 42 during the installation. After the installation is complete and you are ready to configure MP, put the vHBA back into it's correctly configured VSAN.

Or, If you have access to the SAN configuration, you can remove the vHBA/StorageTarget configuration during the install. After installation, put the configuration back in place and activate it.

The single path install is a requirement of Windows Server 2003 and 2008, not UCS.

http://download.microsoft.com/download/f/9/7/f9775acc-baa6-45cc-9dec-b82983705620/Boot%20from%20SAN%20in%20Windows.doc

"Allow a single path to storage when installing the operating system (OS).  For multiple HBA port configurations, only one HBA port should be connected to the SAN during installation.  The same restriction applies to the storage controller ports"

For ESX and RHEL, both paths can be enabled during install. For RHEL, if you don't have both paths enabled during install, it's extra work to bring the second path in after installation.