[linux-lvm] syncing with snapshots takes forever?

Joe Thornber joe at fib011235813.fsnet.co.uk
Fri Jan 24 12:27:01 UTC 2003

On Fri, Jan 24, 2003 at 11:15:15AM -0700, Andreas Dilger wrote:
> The problem is that when you type "sync" you are actually writing (most of)
> your file to disk 4 times - once for the initial LV (which was mostly still
> in RAM I'm guessing), and once for each snapshot.  Since you now have 4x
> the write load and it is not streaming, but random I/O it causes your disks
> to thrash badly.  Add to that the fact that you are writing to a RAID which
> needs to seek _every_ disk for each write, and you are in really bad shape.

30 minutes still seems _far_ too long for LVM2, although totally
reasonable for LVM1.  At the risk of sounding patronising; when you
tried LVM2 are you certain you were not running LVM1 by mistake ?
(eg. was the LVM1 kernel driver present? did your volumes appear in
/dev/mapper/ ?).

- Joe

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