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Special Forums Hardware Filesystems, Disks and Memory Poor read performance on sun storedge a1000 Post 302302357 by TonyFullerMalv on Monday 30th of March 2009 07:00:29 PM
Old 03-30-2009
If a raid 10 made up of 12 disks is 6 disks in a striped volume mirrored against another volume of 6 disks in a striped volume, the the mirroring process (which has to write to both striped volumes) slows down writes compared with reading (which only has to read from one of the striped volumes), normally.

I think writing to /dev/zero is not a good idea, I would try writing to /dev/null instead.

Reading from /dev/random would be interesting to compare with reading from /dev/zero also?
 

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VGREDUCE(8)                                                   System Manager's Manual                                                  VGREDUCE(8)

NAME
vgreduce - reduce a volume group SYNOPSIS
vgreduce [-a|--all] [-A|--autobackup y|n] [-d|--debug] [-h|-?|--help] [--removemissing] [-t|--test] [-v|--verbose] VolumeGroupName [Physi- calVolumePath...] DESCRIPTION
vgreduce allows you to remove one or more unused physical volumes from a volume group. OPTIONS
See lvm for common options. -a, --all Removes all empty physical volumes if none are given on command line. --removemissing Removes all missing physical volumes from the volume group, if there are no logical volumes allocated on those. This resumes normal operation of the volume group (new logical volumes may again be created, changed and so on). If this is not possible (there are logical volumes referencing the missing physical volumes) and you cannot or do not want to remove them manually, you can run this option with --force to have vgreduce remove any partial LVs. Any logical volumes and dependent snapshots that were partly on the missing disks get removed completely. This includes those parts that lie on disks that are still present. If your logical volumes spanned several disks including the ones that are lost, you might want to try to salvage data first by acti- vating your logical volumes with --partial as described in lvm (8). SEE ALSO
lvm(8), vgextend(8) Sistina Software UK LVM TOOLS 2.02.95(2) (2012-03-06) VGREDUCE(8)
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