[linux-lvm] LVM2 Snapshots Question

[linux-lvm] LVM2 Snapshots Question

[Rik Herrin]

Hi,
  I had a question regarding LVM2 snapshots.  I read the following about snapshots (taken from 
http://www.tldp.org/HOWTO/LVM-HOWTO/snapshotintro.html):

"This facility does require that the snapshot be made at a time when the data on the logical volume is in a consistent state - the VFS-lock patch for LVM1 makes sure that some filesystems do this automatically when a snapshot is created, and many of the filesystems in the 2.6 kernel do this automatically when a snapshot is created without patching."

Does this mean that I don't have to unmount (or remount ro) a partition if I'm using a 2.6 kernel to take a snapshot and I can rest assured that the logical volume will be in a consistent state?  Thanks for your help.

Re: [linux-lvm] LVM2 Snapshots Question

[Alasdair G Kergon]

On Sun, Oct 22, 2006 at 04:06:59AM -0700, Rik Herrin wrote:
> Does this mean that I don't have to unmount (or remount ro) a partition if
> I'm using a 2.6 kernel to take a snapshot and I can rest assured that the
> logical volume will be in a consistent state?  Thanks for your help.
 
Yes, in principle; but there was a bug in userspace lvm2 for a while
(fixed in 2.02.08 - introduced around 2.02.02?) and there are problems
with a mistaken semaphone/mutex change someone put into some recent kernels
around 2.6.18.

Alasdair
-- 
agk@redhat.com