[CentOS] pvmove speed

Wed Feb 13 19:15:39 UTC 2008
Ross S. W. Walker <rwalker at medallion.com>

Joseph L. Casale wrote:
> 
> >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...

If the PVs are fault tolerant then I don't know why pvmove
would be running so slow, there should be no io errors being
thrown as the bad drive would be marked as faulty and taken
offline.

What are you pvmoving again?

-Ross

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