[linux-lvm] "Cannot allocate memory" creating VGDA

[linux-lvm] "Cannot allocate memory" creating VGDA

[Paul Warren]

We've now downgraded our server to 2.4 so that we can use snapshotting
in lvm1.  Unfortunately:

woozle:~# lvcreate -s -L3000M -n rootsnapshot  /dev/mainvg/root 

lvcreate -- WARNING: the snapshot will be automatically disabled once it
gets full
lvcreate -- INFO: using default snapshot chunk size of 64 KB for
"/dev/mainvg/rootsnapshot"
lvcreate -- ERROR "Cannot allocate memory" creating VGDA for
"/dev/mainvg/rootsnapshot" in kernel

woozle:~# free
             total       used       free     shared    buffers cached
Mem:       4010688     149192    3861496          0       1824 22944
-/+ buffers/cache:     124424    3886264
Swap:            0          0          0

This is trying to create a snapshot of a 255GB LV.

Any ideas on this one?

cheers,

Paul

Re: [linux-lvm] "Cannot allocate memory" creating VGDA

[Alasdair G Kergon]

On Sat, Oct 16, 2004 at 11:05:47AM +0100, Paul Warren wrote:
> lvcreate -- ERROR "Cannot allocate memory" creating VGDA for
> "/dev/mainvg/rootsnapshot" in kernel

> Any ideas on this one?
 
Ensure the LVM1 part of your kernel is fully patched (there
was a memory over-allocation bug IIRC, but I forget the details).
Try using larger chunk sizes.

Alasdair
-- 
agk@redhat.com

Re: [linux-lvm] "Cannot allocate memory" creating VGDA

[Paul Warren]

On Sat, Oct 16, 2004 at 02:09:29PM +0100, Alasdair G Kergon wrote:
> On Sat, Oct 16, 2004 at 11:05:47AM +0100, Paul Warren wrote:
> > lvcreate -- ERROR "Cannot allocate memory" creating VGDA for
> > "/dev/mainvg/rootsnapshot" in kernel
> 
> > Any ideas on this one?
>  
> Ensure the LVM1 part of your kernel is fully patched (there
> was a memory over-allocation bug IIRC, but I forget the details).
> Try using larger chunk sizes.

Varying the chunk size doesn't seem to help.  This appears to be the
HIGHMEM issue that has come up on the list before.  If we recompile the
kernel without HIGHMEM support, it works OK (apart from the
unavailability of 3/4 of the RAM).

We're running 2.4.27 - are there patches beyond that?

Has anyone had any success with getting snapshots to work on a machine
with > 1GB RAM?

cheers,

Paul

Re: [linux-lvm] "Cannot allocate memory" creating VGDA

[Paul Warren]

On Sat, Oct 16, 2004 at 03:40:45PM +0100, Paul Warren wrote:
> Varying the chunk size doesn't seem to help.  This appears to be the
> HIGHMEM issue that has come up on the list before.  If we recompile the
> kernel without HIGHMEM support, it works OK (apart from the
> unavailability of 3/4 of the RAM).
> 
> We're running 2.4.27 - are there patches beyond that?
> 
> Has anyone had any success with getting snapshots to work on a machine
> with > 1GB RAM?

It seems that this works if you compile the kernel with HIGHMEM 64G
support or with HIGHMEM off, but not with 4G support.

Paul