From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <400F1035.40401@stevek.com> From: Steve Kann MIME-Version: 1.0 References: <400C5158.2000000@stevek.com> In-Reply-To: <400C5158.2000000@stevek.com> Content-Transfer-Encoding: 7bit Subject: [linux-lvm] Re: Cannot create snapshots with kernel 2.4.24, lvm 1.0.4: Cannor allocate memory Sender: linux-lvm-admin@sistina.com Errors-To: linux-lvm-admin@sistina.com Reply-To: linux-lvm@sistina.com List-Help: List-Post: List-Subscribe: , List-Unsubscribe: , List-Archive: Date: Wed Jan 21 18:51:02 2004 List-Id: Content-Type: text/plain; charset="us-ascii"; format="flowed" To: linux-lvm@sistina.com Hi List, Thanks to some helpful off-list help from someone on the list, I've found out that the trouble is related to using LVM with a HIMEM kernel. I have rebuilt a new kernel without himem support, and snapshots are now working. On the other hand, if I run this way, I'll have 3GB of memory basically sitting there doing not much else other than contributing to chassis heat. I also have to get the VFS-Lock patch in there (i'm building a patched kernel now to test it) before snapshots are really useful. So, does anyone either (a) know what the problem is, or (b) at least know where I should look to try and fix it? I'm guessing that the problem has been solved at least by some of the commerical distros.. Thanks. -SteveK Steve Kann wrote: > > > Hi, > > 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 > 521 vgdisplay > 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 gets full > 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: > u2:~# free > 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! > > Any ideas? > > >