Installing Multipath Software

[Jim Druce]

Quick question regarding Multipath software installation, if you've already configured and deployed disks prior to installing Multipath software is there are issues that I need to be aware of when installing the MPIO software... ie should i disconnect the redundant SAN switch before proceeding, and is there any impact on existing SAN disk partitions?

[Ivan Ferreira]

It's extrange that MPIO is not used if you have a production system. You should see multiple disks devices for the sam LUN.

Anyway, you can install the MPIO software at any time, and depending of the software and the operating system, a change may be needed. For example, device names could change for Unix or drive letters for Windows.

There is also a compatibility matrix for MPIO software versions, drivers, sanswitch firmware, and storage firmwares.

[Ben Dehner]

The impact is going to be more on the host then the SAN, and really depends on the host details. Specifically, what host OS, what volume manager (if any), and what MPIO software.

On HP-UX, there's a good chance that the MPIO software will create new device files for your disk. You would need to re-configure your volume groups to use the new device files. You might even need to rebuild the volume groups entirely.

I've less experience with windows, but the MPIO drivers may present the disk as a "new" disk, and claim that the original disk was unavailable. You might have to beat on it to remove the original mappings so the drive letters don't change.

In either case, you'll probably want everything online during the install, so that the MPIO drivers can be properly configured with all of the path data.