[linux-lvm] "cannot allocate memory" when trying to do a snapshot?

[Tomasz Chmielewski <mangoo@wpkg.org>]

I have a server with ~1.5T PV, on which I have several logial volumes (LVs).

I decided to do a snapshot for five of these LVs, and it succeeded, but 
only few times.

   dom-dc1           san1 owi-ao   8.00G
   dom-oss1          san1 owi-ao  16.00G
   dom-sql1          san1 owi-ao   8.00G
   dom-sql1-2        san1 owi-ao  50.00G
   dom-ts1           san1 owi-ao  16.00G

For each of the LVs, I made 5G snapshots.
I could make three snapshots for all of them, but the fourth snapshot 
failed for some LVs (in all, I could only make 18 * 5GB snapshots).

Why?

I'm using Debian Etch, with its 2.6.18 64 bit kernel.
The machine has 512 MB RAM, and 3 GB swap:

# free
              total       used       free     shared    buffers     cached
Mem:        512204     492212      19992          0     297784      17864
-/+ buffers/cache:     176564     335640
Swap:      3145720          0    3145720



I've searched the list, and a similar cases appeared on the list in 
2002/2003, most without any reply - but it was LVM1 / 2.4.x times.


-- 
Tomasz Chmielewski