[Linux-cluster] Clustered VGs with many PVs slow to activate

[Bryn M. Reeves]

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Janne Peltonen wrote:
> Hi.
> 
> There is a clustered vg in my five-node cluster (four of which have
> access to the SAN where the physical devices reside). It seems to me
> that the more LV's and PV's I've got, the more time it takes to get the
> VG activated. When I had 8 PV's and 79 LV's, it took some ten minutes to
> activate the VG on each node. Now, I extended the VG by 39 PV's (so that my

Did you put a metadata copy on each PV? Check with vgdisplay:

  --- Volume group ---
  VG Name               t0
  System ID
  Format                lvm2
  Metadata Areas        4          <---------
  Metadata Sequence No  3
  VG Access             read/write
  VG Status             resizable
  MAX LV                0
  Cur LV                0
  Open LV               0
  Max PV                0
  Cur PV                64
  Act PV                64
  VG Size               7.75 GB
  PE Size               4.00 MB
  Total PE              1984
  Alloc PE / Size       0 / 0
  Free  PE / Size       1984 / 7.75 GB
  VG UUID               PcERts-A1MU-KoT6-gu6R-Acuw-MYuf-08Ximv

If that's the case, you probably don't want one for each PV here. It's
unnecessary and will slow the tools down a lot when there are a large
number of PVs.

Check out the --metadatacopies option to pvcreate and re-create the
volume group with a much smaller number of MDAs if this is the problem
you're seeing. If you're careful you can do this in-place via the
- --restorefile option to pvcreate and vgcfgbackup/vgcfgrestore.

Regards,
Bryn.

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