Re: Domain saving and filesystem corruption

[Tracy R Reed <treed@ultraviolet.org>]

Anthony Liguori wrote:
> You really ought to avoid save/restore/migrate when not using network or 
> checkpointable storage.  You will almost certainly eventually get some 
> sort of corruption.

No doubt. Thing is, I didn't realize it was doing this. The machine so 
rarely gets rebooted that I never noticed it saving out the state of the 
domains to disk. I am impressed with how fast it does it though.

> I didn't realize xend actually tries to save domains on shutdown.  Seems 
> like a bad idea to me.  Is this correct?  Is this only for domains 
> started with /etc/init.d/xendomains?

On RedHat (I run FC5 in my domain0 and CentOS 4.3 in my domains) you can 
look in /etc/sysconfig/xendomains to see how this all works. It looks 
like by default it will try to save the state of all domains unless you 
set XENDOMAINS_AUTO_ONLY to true. It is set to false by default.

One odd thing I see is this:

# Directory to save running domains to when the system (dom0) is
# shut down. Will also be used to restore domains from if
# XENDOMAINS_RESTORE
# is set (see below). Leave empty to disable domain saving on shutdown
# (e.g. because you rather shut domains down).
# If domain saving does succeed, SHUTDOWN will not be executed.
#
#XENDOMAINS_SAVE=/var/lib/xen/save

So XENDOMAINS_SAVE is commented out by default. So it should be "". So 
why are the domains being saved? It looks like it should not have 
defaulted to trying to save all of the domains but it should have 
skipped saving them since XENDOMAINS_SAVE is not defined and it should 
have executed the commands in XENDOMAINS_SHUTDOWN. I am not in front of 
my Xen console right now where I can play with this but I will try to 
look into it tonight when I am.

-- 
Tracy R Reed                  http://ultraviolet.org
A: Because we read from top to bottom, left to right
Q: Why should I start my reply below the quoted text