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Subject: Re: [linux-lvm] Creating snapshot on / hangs machine
From: Clint Byrum <cbyrum@spamaps.org>
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Date: Thu, 14 Oct 2004 11:19:23 -0700
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On Thu, 2004-10-14 at 13:16 -0500, Andrew W. Donoho wrote:
> 
> 
> ______________________________________________________________________
> 
> 
> On Oct 14, 2004, at 11:31, Kai Leibrandt wrote:
>         As soon as I create a snapshot on / however, the machine
>         hangs, although X still works (well, the mouse still moves),
>         it is no longer possible to open a new shell, switch consoles,
>         or even <CTRL>C the lvcreate.
>         
>         I have tried this with ext2 as well as with xfs, including
>         doing xfs_freeze before taking the snapshot, so I don't think
>         it's a filesys related matter.
>         
>         Is there anything I am missing here? Is it even supported to
>         do / snapshots?
> 
> 
> Kai,
> 
> I reported a similar problem starting with my root partition when I
> added a second drive. After a bit of skullduggery, I believe that LVM
> activities on the root partition particularly stress the memory
> system. Or, at least, when I slowed the memory system down on my
> x86-64 machine, I no longer get crashes like you describe above. 
> 


Weird.. I thought the problem was that LVM was causing the atime on
the /dev entries to be updated, which required write access, but there
was a lock on the filesystem while the snapshot was created.