[Libvir] Re; virDomainBlockStats

Gareth Bult gareth at encryptec.net
Sat Jan 26 23:29:54 UTC 2008

Mmm, Ok ..

I've pretty much spent the last week getting Xen 3.2 to function "properly" built entirely from raw XEN sources using  Xen's documentation. AIO is still a flakey as hell, one time through the loop and the instance seems to work, second time around it won't start and neither will anything else.

I have file: based instances running just fine .. my guess is the unload problem is still there, but the kernel logging is 
gone and they've created a critical system lock-up in it's place.

Is there any documentation to the effect that "file" is bad??
The official XEN documentation lists "file" as the standard and makes no mention of "aio".

Currently I'm mounting my image on gluster filesystems and I'm getting 70Mb/sec so I'm not unhappy with the performance, and I've had no issues recently with crashes. ... more information would be useful if you have it.

Whereas I'm happy to accept that aio is better in principle, as far as I can see although it may work for you, I've now tried it in a number of different configurations on a number of machines and it's simply unusable.


----- Original Message -----
step 3.: "Daniel P. Berrange" <berrange at redhat.com>
To: "Gareth Bult" <gareth at encryptec.net>
Sent: 19 January 2008 17:50:01 o'clock (GMT) Europe/London
Subject: Re: [Libvir] Re; virDomainBlockStats

On Sat, Jan 19, 2008 at 05:18:58PM +0000, Gareth Bult wrote:
> Mmm,
> Interesting ..
> First off, xentop doesn't display block device stats for tap:aio based systems and it does for file.
> Second, tap:aio generated kernel Ooops's when you shutdown a DomU.
> Not exactly what I'd call mainstream (!)

That must be a flaw in Ubuntu's kernels. tap:aio works flawlessly
in Fedora / RHEL and is the only supported option, because file:
has catastrophic data loss issues during host crashes.

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