[linux-lvm] Snapshot Problem JFS

Heinz J . Mauelshagen mauelshagen at sistina.com
Fri Jun 20 04:23:01 UTC 2003

On Thu, Jun 19, 2003 at 09:07:30PM -0500, David Sornig wrote:
> I am running RedHat 9.0
> Kernel 2.4.20-8
> LVM Version 1.0.5+(22/07/2002)
> I have a 1.4T LogVol with 400G of space being used on a JFS file system.
> The LVM is working excellent.  However,  I cannot create a snapshot.  I run the following lvcreate command as per the man page and get the following error:
> lvcreate --error "Cannot allocate memory"  creating VGDA for "/dev/Volume00/snap01" in kernel


memory allocated to the snapshot needs free physical RAM.

With 400GB and default snapshot extent size we're talking about ~1GB
(using virtual memory for snapshot exception tables so that the table doesn't
need to be in RAM completely any longer is a work item for LVM2).

Do you really expect that much change to your 1.4TB LV during the lifetime of
the snapshot ?
If you use it for a backup, you might get along with a couple of GB allocated
to the snapshot reducing exception table size drastically.

> Not sure why this is happening.  I have read the list and maybe I just don't understand the problem.  These servers have 4 Gigs of RAM.
> Regards,
> David


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
Mauelshagen at Sistina.com                           +49 2626 141200
                                                       FAX 924446

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