Re: Very slow LVM performance

[Stan Hoeppner <stan@hardwarefreak.com>]

Roger Leigh put forth on 7/12/2010 5:45 PM:

> Have a closer look at lvcreate(8).  The last arguments are:
> 
>        [-Z|--zero y|n] VolumeGroupName [PhysicalVolumePath[:PE[-PE]]...]

Good catch.  As I said I've never used it before, so I wasn't exactly sure how
it all fits.  Seemed logical that when he went from testing the mdadm device
to the lvm volume and lost almost exactly 10x that a striping issue wrt lvm
may be in play.

> AFAICT the striping options are entirely pointless when layered on
> RAID, and could be responsible for the performance issues if it
> can have a negative impact (such as thrashing the disks if you
> tell it to write multiple stripes to a single disc).

I would have thought so as well, but didn't understand the exact function of
-i at the time.  I thought it was more like the xfs "-d sw=" switch.

>From another post it looks like the OP is making some good progress, although
there are still some minor questions unanswered.

-- 
Stan