[linux-lvm] snapshot on root file system

Nix nix at esperi.org.uk
Sun Jan 7 00:41:09 UTC 2007

On 2 Jan 2007, jjletho67-mvl at yahoo.it outgrape:
> Searching around about this problem I found that also
> other lvm users suffer of a similar problem when the
> root partition is involved, but I was unable to
> understand what is the cause of the problem and if
> there is a way to avoid it. Does LVM really support
> root partition ? Does the problem involves only
> snapshot or also other aspetcs ? Workaround ?

My understanding is that snapshot creation involves a brief period when
I/O to the origin LV is suspended: if lvcreate needs to page in
something from that device, or needs to read, say, /etc/lvm/lvm.conf,
or something, you'll get a deadlock.

(Mind you this all seems fixable to me: before suspending, mlockall()
lvcreate in memory, touch all its pages to force pagein, and do all
other reading required. But I guess this just hasn't been done yet.)

`He accused the FSF of being "something of a hypocrit", which
 shows that he neither understands hypocrisy nor can spell.'
   --- jimmybgood

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