alternate paths

[Brian Street_1]

Hello,

Question on the setup of alternate paths...

if vgdisplay -v shows an alternate path for a disk device, does that automatically mean that if the primary scsi path fails it automatically accesses the disk through the alternate path...

or do I have to vgextend the lvm to the second disk to get the automatic failover?

Thanks,
Brian.

[James Murtagh · Accepted solution]

Hi Brian,

If vgdisplay shows the alternate path it must already have been added to the volume group by vgextend. So yes, if the primary path fails it will switch over.

Regards,

James.

[Brian Street_1]

James,

Thank you for confirming my thoughts.

Brian.

[Eugeny Brychkov]

hpux supports 7 alternate paths (+1 primary = 8 paths) - it's applicable in SAN envirnment, where host can see LUN more than 2 times (1 pri + 1 alt). These paths are used in order as they appear in vgdisplay output: if primary fails, 1st alternate is used, if this 1st alternate will fail then 2nd is used and so on.
Good thing that you can use PV 'load balancing' across paths, for example if you have 2 PVs stirped within one VG you setup path1 as primary for PV1 and path2 as alernate and path2 as primary for PV2 and path1 as alternate
Eugeny