[CentOS] pvmove speed

[Joseph L. Casale]

>I don't believe pvmove actually does any of the lifting. Pvmove
>merely creates a mirrored pv area in dev-mapper and then hangs
>around monitoring it's progress until the mirror is sync'd up
>then it throws a couple of barriers and removes the original
>pv from the mirror leaving the new pv as the new location for
>the data.
>
>That is how the move continues through reboots. All lifting
>is actually done in dev-mapper and it's state is preserved
>there. On restart LVM will read it's meta-data to determine
>if there is a pvmove in progress and then spawn a pvmove to
>wait for it to complete so it can remove the mirror.
>
>Any slowness is due to disk io errors and retries being
>thrown around.
>
>You should really run LVM on top of a RAID1, software or
>hardware makes no difference, but LVM is more to storage
>management then fault tolerance and redundancy.
>
>-Ross

The LD's provided to LVM through the RAID controller are all fault tolerant...

Good info, Thanks!
jlc