Dave Costakos wrote:
> I'm trying to troubleshoot a problem where mkfs commands take a really,
> really long time to complete in my Xen guests.
>
> I'm using sparse file-backed images created using the 'virt-install' command
> on RHEL 5.1 x86_64. I'm kickstarting paravirtualized RHEL 4.5 and 5.1
> x86_64 guests and they are going through a standard, unattended install with
> a common diskmap. When they get to formatting the various local disks, all
> file system formats are taking unfeasibly long. A 20+ GB file system takes
> upwards of 20 minutes to run an mkfs on. During the mkfs, the underlying
> filesystem on the DOM0 shows high utilization via iostat (upwards on 99%
> utilization), but still the mkfs is horribly, horribly slow. mkfs is
> horribly slow whether I use a GFS, ext3 or NFS underlying filesystem, so I
> don't think that is the issue here.
>
> If I create a non-sparse disk image or a physical partition or logical
> volume, formatting times are drastically increased. However, I'm trying to
> be judicious with overall storage utilization and flexibility, I would very
> much like to stick with sparse files.
>
> Any advice on how I can troubleshoot this further or possibly find a
> solution? Is there another local disk driver I can use besides "tap:aio"
> (like "file") during the install process?
>
> Note: My underlying storage devices are Fibre Channel Hitachi OPEN-V*3
> disks if it helps at all.

What about the rest of the system? CPU, RAM? Do you have local disk you
can try on?

Your performance problem sounds like stuff isn't being cached when it
should be; one explanation would be lack of RAM, others might be slow
disk or some tuning options set wrongly.

Just to mark the bench, are you able to try this under Windows using
Virtual PC and/or Virtual Server (both free downloads from Microsoft)?

--

Cheers
John

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