Re: [Xen-API] Guests running slowly after restart?

[Denis Cardon <denis.cardon@xxxxxxxxxxxxxxxxxxxxxx>]

Hi dswartz,

> Hopefully this is the right list for this, if not my apologies.  Anyway, I
> am running XCP 1.6 on a xeon e3-1230 with 24MB RAM.  A handful of guests,
> all but one of which are HVM (mainly because of lack of a good tool to PV
> such guests) previously running under KVM.  One is windows 7 the others
> various flavors of linux.  Anyway, I rebooted one of the guests (Astaro
> Security Gateway) after an update.  It started booting, but very very
> slowly.  Took almost 10 minutes to get a login prompt, when it usually
> takes less than a minutes.  Once I was in, 'w' revealed a load factor of 8
> or so, which was increasing as I was watching.  It wasn't (obviously)
> paging, and oddly, xencenter claimed the guest was using 3% of 1 vCPU.  I
> ended up having to reboot the host at which point all was well.  The same
> thing happened about 12 hours later, at which point I tried restarting 2
> of the other linux guests and saw the exact same behavior, so it wasn't
> just ASG.  Again, a reboot 'fixed' this.  I have limited data points here,
> but the problem seems to occur when (after some unknown amount of time), I
> try to restart a guest.  Note that prior to restarting them, the guests
> seem to be running just fine.  I am relatively new to Xen, so any clues
> would be appreciated.  Thanks!
Could you check that iowait (the %wa in top) is not the culprit? That 
could explain that cpu consumption was low.
Not having PV drivers have a huge impact on disk and network io. CPU and 
mem will be fine, but if you have some process that have heavy io 
pattern, they can be brought to a crawl.
If your vms are not too old (2.6.18 and higher), you should probably try 
to switch to paravirt. For kernel <2.6.24, you'll have to select a 
specific xen enabled kernel, for more recent kernel it should work out 
of the box. You can follow the doc on 
http://forums.citrix.com/message.jspa?messageID=1005837
When switching to paravirt, your default console may switch to hvc0 and 
your drive names to xvdx, so check your grub, /etc/inittab and /etc/fstab.
Hope this helps,

Denis





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--
Denis Cardon
Tranquil IT Systems
Les Espaces Jules Verne, bâtiment A
12 avenue Jules Verne
44230 Saint Sébastien sur Loire
tel : +33 (0) 2.40.97.57.55
http://www.tranquil-it-systems.fr


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