Tomasz Chmielewski schrieb:
Ouch - now it went so far that the machine only loops from a kernel
panic to a kernel panic - that's really bad:
(...)
Out of memory: kill process 2220 (getty) score 24 or a child
Killed process 2220 (getty)
Kernel panic - not syncing: Out of memory and no killable processes...
Rebooting in 20 seconds..
Again, replying to myself, as no one on this list seem to have a clue
about problems with LVM snapshots... I added RAM, and was able to boot
again.
Below is a quick try to estimate the memory usage of LVM snapshots; I'm
using 2.6.22.6.
The machine has 256 MB RAM.
With these volumes and snapshots, almost 200 MB of memory is used:
# lvs
LV VG Attr LSize Origin Snap% Move Log
Copy%
backup st owi-ao 1.20T
backup-snap st swi-a- 100.00G backup 31.22
backup-snap-resized st swi-a- 30.00G backup 72.73
backup1 st -wi-a- 3.00G
backup1-sync-test st -wi-a- 3.00G
src st -wi-a- 2.00G
swap st -wi-ao 3.00G
# free
total used free shared buffers cached
Mem: 512864 418380 94484 0 216036 5156
-/+ buffers/cache: 197188 315676
After removing a 100 GB snapshot that is over 30% full, we reclaim
almost 100 MB of memory:
# lvremove /dev/st/backup-snap
Do you really want to remove active logical volume "backup-snap"? [y/n]: y
Logical volume "backup-snap" successfully removed
# free
total used free shared buffers cached
Mem: 512864 328668 184196 0 220652 7480
-/+ buffers/cache: 100536 412328
Swap: 3145720 220 3145500
After removing yet another snapshot - 30 GB, over 70% full - we reclaim
70 MB:
# lvremove /dev/st/backup-snap-resized
Do you really want to remove active logical volume
"backup-snap-resized"? [y/n]: y
Logical volume "backup-snap-resized" successfully removed
# free
total used free shared buffers cached
Mem: 512864 335500 177364 0 296444 9436
-/+ buffers/cache: 29620 483244
Swap: 3145720 216 3145504
So, as a rule of thumb, we can say that for each *used* GB of snapshot,
~3 MB of RAM is needed.
--
Tomasz Chmielewski
http://wpkg.org
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