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Top Forums UNIX for Dummies Questions & Answers SAN and Disk I/O ... do we care? Post 302454945 by jim mcnamara on Monday 20th of September 2010 10:51:54 AM
Old 09-20-2010
Normally a logical volume (lun) is based on all of the disks in a given SAN device. You do not tell the SAN where to store a lun. Period.

The SAN software can be confiured for different types of RAID settings and SAN software does all sorts of tuning and caching. If what you saw is WAY out of line, ask your disk guy to monitor what is going on. He/she can make adjustments.

The "disk" stuff you see df -h or iostat in the OS is the logical presentation of a filesystem on the OS, never a single physical disk. Don't conflate logical volumes and physical disks, which is what you seem to be doing.
 

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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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