Workiis: pvmove problem

I am using LVM2 with linux 2.6.11. One of the drive in the volume is going bad. I could hear screeching noise while the platters were spinning.

That is bad. Not a problem, though, as I can just vacate the data from that drive using pvmove.
The bad drive is /dev/bad. /dev/avail is a volume with some free space.

# pvdisplay /dev/bad /dev/avail
  --- Physical volume ---
  PV Name               /dev/bad

VG Name               vg0
  PV Size               148.09 GB / not usable 0
  Allocatable           yes
  PE Size (KByte)       4096
  Total PE              37911
  Free PE               25111
  Allocated PE          12800
  PV UUID               e5EvaO-0oo5-Zenl-KzkY-wFf7-EkQX-di1mXt

  --- Physical volume ---
  PV Name               /dev/avail

VG Name               vg0
  PV Size               186.30 GB / not usable 0
  Allocatable           yes
  PE Size (KByte)       4096
  Total PE              47694
  Free PE               20658
  Allocated PE          27036
  PV UUID               HLtCMK-751U-IFAW-5Aj3-FQ3w-5tqO-8svvwt

Let's move it to the only drive with available space, /dev/avail. /dev/bad has 12800 allocated PE while /dev/avail has 20658 free PE. I was not expecting any problem fitting the data in /dev/bad into /dev/avail.

# pvmove -i 5 -v /dev/bad

Finding volume group "vg0"
    Archiving volume group "vg0" metadata.
    Creating logical volume pvmove0
    Moving 0 extents of logical volume vg0/lv0

Insufficient contiguous allocatable extents (1777) for logical
    volume pvmove0: 12800 required
  Unable to allocate temporary LV for pvmove.

Urk? It needs to be contiguous? What to do now?

Searching through the lvm mailing list shows that pvmove is dumb. It only sees the first free PE (physical extent). OK, let's work around this.

# vgcfgbackup

# grep pv0 /etc/lvm/backup/vg0
                pv0 {
                                        "pv0", 30720
                                        "pv0", 0
                                        "pv0", 17920

pv0 is the physical volume corresponding to /dev/bad. From this, we see that there are three segments residing in pv0. The first starts at PE 30720.

Let's try to fill that 1777 free PE on the dest drive, /dev/avail. That means, we'll be moving PE 30720 to (30720+1777-1=32496) from pv0.

# pvmove -i 5 -v /dev/bad:30720-32496
    Finding volume group "vg0"
    Archiving volume group "vg0" metadata.
    Creating logical volume pvmove0
    Moving 0 extents of logical volume vg0/lv0

Moving 1777 extents of logical volume vg0/lv1
    Moving 0 extents of logical volume vg0/lv2

Moving 0 extents of logical volume vg0/lv3
    Found volume group "vg0"
    Updating volume group metadata
    Creating volume group backup "/etc/lvm/backup/vg0"
    Found volume group "vg0"
    Found volume group "vg0"
    Loading vg0-pvmove0
    Found volume group "vg0"
    Loading vg0-lv1

Checking progress every 5 seconds
  /dev/hdf2: Moved: 7.7%
  /dev/hdf2: Moved: 14.4%
  /dev/hdf2: Moved: 22.6%
  /dev/hdf2: Moved: 29.7%
  /dev/hdf2: Moved: 37.4%
  /dev/hdf2: Moved: 44.6%
  /dev/hdf2: Moved: 52.3%
  /dev/hdf2: Moved: 60.0%
  /dev/hdf2: Moved: 67.7%
  /dev/hdf2: Moved: 75.4%
  /dev/hdf2: Moved: 83.1%
  /dev/hdf2: Moved: 90.3%
  /dev/hdf2: Moved: 97.4%
  /dev/hdf2: Moved: 100.0%
    Found volume group "vg0"
    Found volume group "vg0"
    Found volume group "vg0"
    Loading vg0-pvmove0
    Found volume group "vg0"
    Loading vg0-lv1

    Found volume group "vg0"
    Found volume group "vg0"
    Removing temporary pvmove LV
    Writing out final volume group after pvmove
    Creating volume group backup "/etc/lvm/backup/vg0"

Finally, after repeating the above process for the remaining segments, /dev/bad, aka pv0, is free of data and is safe to take down.

# vgreduce vg0 /dev/bad

Toss it in the garbage bin.

(originally from http://microjet.ath.cx/WebWiki/pvmove%20problem.html)

Workiis

2005-08-23

pvmove problem

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