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Re: [Xen-users] Frequent para (Linux) domU hangs

Hi Nathan, all,

One thing I've just noticed: the two domU's that are frequently hanging
are doing serious (database) I/O from time to time (not always but in
bursts). Both have a relatively high VBD_OO, the domU that just hung had
a VBD_OO of over 800 while the other domU's have very low VDB_OO (4 or 32).

I found this on the Internet:


Basically Satoshi suggests in his email that the underlying hardware is
not able to keep up with the I/O requests of these particular domU's (if
I read him well).

I wouldn't mind if the domU's simply slowed down if the hardware can't
keep up... but in my case once they get "there", they hang and do not
seem to return to normal (well we can't afford to wait for days).

Any suggestions to further diagnose (and fix? :-) ) this problem are
very welcome.

kind regards,

Jan Bakuwel wrote:
> Hi Nathan,
>> Dom0 is Debian Etch amd64 (haven't upgraded this Dom0 yet) running 
>> 2.6.26-bpo.1-xen-amd64.  Xen version is xen-3.2-1-amd64.  Plenty of leftover 
>> memory and swap.
>> DomU is Centos 5.3 Final amd64, running the dom0's kernel 
>> (2.6.26-bpo.1-xen-amd64).  DomU has lots of memory and plenty of swap (added 
>> because I suspected it may have been a problem).
>> One possibility I am beginning to suspect is that domU may be filling up 
>> /tmp (using /usr/tmpDSK for some reason).  Not sure on that, though.  I may 
>> try removing that from the fstab and see if stability improves...
> Seems like we're in a similar although not identical environment.
> I think there's not much difference (or perhaps none at all) between the
> backported etch kernel and the lenny kernel?
> I've planned an upgrade to 2.6.26-2-xen-amd64 in the next few weeks to
> see if that makes a difference and have just added a swapfile to one of
> the two troubled VMs.
> Please keep me informed about your progress; I'll do the same.
> Jan
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