3ea86f7d60
This patch changes how we discover Multipath devices for FibreChannel volume attaches. Running multipath -l <device> can become slower and slower as more and more volumes are attached to a host. To overcome this, there are ways of discovering multipath device paths without using the multipath -l command at all. When multipath daemon is running, and it discovers new volumes, it will create new device paths for the multipath device associated with that new volume. Those multipath device paths are predictable and show up after the multipath device is created. This avoids the repeated looping calls to multipath -l to discover the same paths. SCSI volumes have a WWN that's supposed to be in page 0x83 on the volume itself according to the SCSI SPC-3 spec. That WWN is where the multipath daemon gets it's multipath ID from and what is used to create the predictable multipath device paths on the system. When multipath friendly names are disabled, you get paths of /dev/disk/by-id/dm-uuid-mpath-<WWN> /dev/disk/by-id/scsi-<WWN> /dev/mapper/<WWN> When multipath friendly names are enabled, you get paths of /dev/disk/by-id/dm-uuid-mpath-<WWN> /dev/disk/by-id/dm-name-mpath<N> /dev/disk/by-id/scsi-mpath<N> /dev/mapper/mpath<N> This patch does 3 different attempts to find a multipath device path to use. First it looks in the common location of: /dev/disk/by-id/dm-uuid-mpath-<WWN> Then in the non friendly name path of: /dev/mapper/<WWN> And lastly using the fallback of calling multipath -l <device> to get: /dev/mapper/mpath<N> Partial-Bug: 1487169 Change-Id: I9a9fffcb6882b1c2750b1e7927475093bde36d04 |
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| rootwrap.d | ||