[linux-lvm] Cannot create snapshots with kernel 2.4.24, lvm 1.0.4: Cannor allocate memory
stevek at stevek.com
Mon Jan 19 16:59:01 UTC 2004
I've seen some others on this (and other lists) who are having this
problem, but I haven't been able to find a solution.
I have a new box that I'd like to use with LVM. This will be a
production fileserver. I've installed debian woody on it, and upgraded
to the latest debian kernel, 2.4.24. I'm using the lvm 1.0.4 tools.
Naturally, I'm spending this time before this box is in use to play
with LVM so I know how to do what I need to quickly before the fires
hit. So, I've been able to happily create, grow, shrink, and remove
lv's, as well as create and remove VGs and PVs.
However, I cannot create a snapshot volume.
This is pretty much why I wanted to use LVM in the first place
(backing up a 400G active filesystem would be pretty impossible otherwise).
The basic error I get is:
520 vgcreate -s 128M vg0 /dev/sda7
522 lvcreate -L 256M -nhome vg0
u2:~# lvcreate -s -L128M -c 4k -nhomesnap /dev/vg0/home
lvcreate -- WARNING: the snapshot will be automatically disabled once it
lvcreate -- ERROR "Cannot allocate memory" creating VGDA for
"/dev/vg0/homesnap" in kernel
Other snapshot creation attempts, all of which fail the same way:
525 lvcreate -s -L1M -nhomesnap /dev/vg0/home
526 lvcreate -s -L128M -c 1M -nhomesnap /dev/vg0/home
I've tried making a bunch of different volumes on which to base the
snapshot, as well as a number of different parameters for the snapshot
itself. I thought that perhaps it couldn't handle snapshots that were
larger than a certain size, or snapshots of volumes that are beyond a
certain size, etc.
I should have plenty of memory:
total used free shared buffers cached
Mem: 4010744 111160 3899584 0 18444 58084
-/+ buffers/cache: 34632 3976112
Swap: 2097136 0 2097136
If 3.8GB of Real, or 5.8 GB of virtual memory aren't actually enough to
create a 128MB snapshot of a 256Mb volume (I tried making it very
small!), then something must be very wrong!
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