[linux-lvm] Error creating snapshot, "Cannot allocate memory"

[linux-lvm] Error creating snapshot, "Cannot allocate memory"

[jheiss-linuxlvm]

I have a volume group that is 1.4 TB, with a volume that is 400 GB.
I currently have three 50 GB snapshots of that volume.  When I try
to create a fourth, I get the following error:

bash-2.05a# lvcreate -L 50G -s -n snap_home1_20021202 /dev/home/home1
lvcreate -- WARNING: the snapshot will be automatically disabled once it
gets full
lvcreate -- INFO: using default snapshot chunk size of 64 KB for
"/dev/home/snap_home1_20021202"
lvcreate -- ERROR "Cannot allocate memory" creating VGDA for
"/dev/home/snap_home1_20021202" in kernel

After some experimenting, I found that I could create a snapshot that
is 36 GB or smaller, but anything larger than 36 GB fails with the above
error.  The volume group has 386 GB free.

Any thoughts?  I looked through the changelog and mailing list archives
and couldn't find anything similar.

Other possibly useful bits of info:

OS:  Red Hat 7.3
kernel:  2.4.18-18.7.xsmp
LVM:  1.0.3-4  (Red Hat RPM)

Jason

Re: [linux-lvm] Error creating snapshot, "Cannot allocate memory"

[Heinz J . Mauelshagen]

On Mon, Dec 02, 2002 at 02:32:23PM -0800, jheiss-linuxlvm@ofb.net wrote:
> I have a volume group that is 1.4 TB, with a volume that is 400 GB.
> I currently have three 50 GB snapshots of that volume.  When I try
> to create a fourth, I get the following error:
> 
> bash-2.05a# lvcreate -L 50G -s -n snap_home1_20021202 /dev/home/home1
> lvcreate -- WARNING: the snapshot will be automatically disabled once it
> gets full
> lvcreate -- INFO: using default snapshot chunk size of 64 KB for
> "/dev/home/snap_home1_20021202"
> lvcreate -- ERROR "Cannot allocate memory" creating VGDA for
> "/dev/home/snap_home1_20021202" in kernel

You don't have enough kernel virtual memory to hold the snapshot exception
table in core :(
Install more RAM.

We have planned to reduce the amount of RAM needed to hold such tables
in LVM2/device-mapper next year.

> 
> After some experimenting, I found that I could create a snapshot that
> is 36 GB or smaller, but anything larger than 36 GB fails with the above
> error.  The volume group has 386 GB free.
> 
> Any thoughts?  I looked through the changelog and mailing list archives
> and couldn't find anything similar.
> 
> Other possibly useful bits of info:
> 
> OS:  Red Hat 7.3
> kernel:  2.4.18-18.7.xsmp
> LVM:  1.0.3-4  (Red Hat RPM)
> 
> Jason
> 
> 
> _______________________________________________
> linux-lvm mailing list
> linux-lvm@sistina.com
> http://lists.sistina.com/mailman/listinfo/linux-lvm
> read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/

-- 

Regards,
Heinz    -- The LVM Guy --

*** Software bugs are stupid.
    Nevertheless it needs not so stupid people to solve them ***

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-

Heinz Mauelshagen                                 Sistina Software Inc.
Senior Consultant/Developer                       Am Sonnenhang 11
                                                  56242 Marienrachdorf
                                                  Germany
Mauelshagen@Sistina.com                           +49 2626 141200
                                                       FAX 924446
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-

Re: [linux-lvm] Error creating snapshot, "Cannot allocate memory"

[Jon Bendtsen]

"Heinz J . Mauelshagen" wrote:
> 
> On Mon, Dec 02, 2002 at 02:32:23PM -0800, jheiss-linuxlvm@ofb.net wrote:
> > I have a volume group that is 1.4 TB, with a volume that is 400 GB.
> > I currently have three 50 GB snapshots of that volume.  When I try
> > to create a fourth, I get the following error:
> >
> > bash-2.05a# lvcreate -L 50G -s -n snap_home1_20021202 /dev/home/home1
> > lvcreate -- WARNING: the snapshot will be automatically disabled once it
> > gets full
> > lvcreate -- INFO: using default snapshot chunk size of 64 KB for
> > "/dev/home/snap_home1_20021202"
> > lvcreate -- ERROR "Cannot allocate memory" creating VGDA for
> > "/dev/home/snap_home1_20021202" in kernel
> 
> You don't have enough kernel virtual memory to hold the snapshot exception
> table in core :(
> Install more RAM.

I've seen this error as well. In a machine with 1GB memory and the only
processes
running were NFS and samba. Just how much memory does it need ?

 
> We have planned to reduce the amount of RAM needed to hold such tables
> in LVM2/device-mapper next year.

That would be nice.




JonB

Re: [linux-lvm] Error creating snapshot, "Cannot allocate memory"

[Jason Heiss]

On Tue, Dec 03, 2002 at 12:52:35PM +0100, Jon Bendtsen wrote:
> "Heinz J . Mauelshagen" wrote:
> > 
> > You don't have enough kernel virtual memory to hold the snapshot exception
> > table in core :(
> > Install more RAM.
> 
> I've seen this error as well. In a machine with 1GB memory and the only
> processes
> running were NFS and samba. Just how much memory does it need ?
> 

Indeed, my server has 2 GB of RAM and 1 GB of swap, of which free
reports only a few hundred MB in use.

Jason

Re: [linux-lvm] Error creating snapshot, "Cannot allocate memory"

[Heinz J . Mauelshagen]

On Tue, Dec 03, 2002 at 10:21:20AM -0800, Jason Heiss wrote:
> On Tue, Dec 03, 2002 at 12:52:35PM +0100, Jon Bendtsen wrote:
> > "Heinz J . Mauelshagen" wrote:
> > > 
> > > You don't have enough kernel virtual memory to hold the snapshot exception
> > > table in core :(
> > > Install more RAM.
> > 
> > I've seen this error as well. In a machine with 1GB memory and the only
> > processes
> > running were NFS and samba. Just how much memory does it need ?
> > 
> 
> Indeed, my server has 2 GB of RAM and 1 GB of swap, of which free
> reports only a few hundred MB in use.

Hmmm...

vmalloc() fails to allocate kernel virtual memory. That's why you get the
error. Could well be a constraint in vmalloc() in general or in the
Redhat kernel you use.
Have you tried using a 2.4.20 vanilla kernel and were able to reproduce this
(enough free RAM presumed).

> 
> Jason
> 
> 
> _______________________________________________
> linux-lvm mailing list
> linux-lvm@sistina.com
> http://lists.sistina.com/mailman/listinfo/linux-lvm
> read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/

-- 

Regards,
Heinz    -- The LVM Guy --

*** Software bugs are stupid.
    Nevertheless it needs not so stupid people to solve them ***

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-

Heinz Mauelshagen                                 Sistina Software Inc.
Senior Consultant/Developer                       Am Sonnenhang 11
                                                  56242 Marienrachdorf
                                                  Germany
Mauelshagen@Sistina.com                           +49 2626 141200
                                                       FAX 924446
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-

[linux-lvm] ERROR creating snapshot: "Cannot allocate memory"

[Murthy Kambhampaty]

While trying to snapshot a 335 GB LV (sdd1) on a machine with 12 GB of RAM,
and 67 GB of free space (sdc1), I get the following error:

lvcreate -s -l 21 -n snapshot /dev/VGdb01/LVdb
lvcreate -- WARNING: the snapshot will be automatically disabled once it
gets full
lvcreate -- INFO: using default snapshot chunk size of 64 KB for
"/dev/VGdb01/snapshot"
lvcreate -- ERROR "Cannot allocate memory" creating VGDA for
"/dev/VGdb01/snapshot" in kernel

kernel is 2.4.21 (LVM 1.0.5+) with tools form
~redhat/contrib/lvm-1.0.5.src.rpm

Help

RE: [linux-lvm] ERROR creating snapshot: "Cannot allocate memory"

[Little, Chris]

good luck getting help on snapshot.  i've posted a couple of times and
haven't gotten a response.  It's buggy and it corrupts data.  don't use it.

> -----Original Message-----
> From: Murthy Kambhampaty [mailto:murthy.kambhampaty@goeci.com]
> Sent: Wednesday, December 03, 2003 4:22 PM
> To: 'linux-lvm@sistina.com'
> Subject: [linux-lvm] ERROR creating snapshot: "Cannot allocate memory"
> 
> 
> While trying to snapshot a 335 GB LV (sdd1) on a machine with 
> 12 GB of RAM,
> and 67 GB of free space (sdc1), I get the following error:
> 
> lvcreate -s -l 21 -n snapshot /dev/VGdb01/LVdb
> lvcreate -- WARNING: the snapshot will be automatically 
> disabled once it
> gets full
> lvcreate -- INFO: using default snapshot chunk size of 64 KB for
> "/dev/VGdb01/snapshot"
> lvcreate -- ERROR "Cannot allocate memory" creating VGDA for
> "/dev/VGdb01/snapshot" in kernel
> 
> kernel is 2.4.21 (LVM 1.0.5+) with tools form
> ~redhat/contrib/lvm-1.0.5.src.rpm
> 
> Help
> 
> _______________________________________________
> linux-lvm mailing list
> linux-lvm@sistina.com
> http://lists.sistina.com/mailman/listinfo/linux-lvm
> read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
>