Zavodsky, Daniel (GE Money) wrote:
>   Sparse files are really bad... not only it takes ages to mkfs on

??

16:29 [summer@(protected)
0+0 records in
0+0 records out
0 bytes (0 B) copied, 5.1e-05 seconds, 0.0 kB/s
16:29 [summer@(protected)

real   1m16.787s
user   0m0.076s
sys   0m9.353s
16:31 [summer@(protected)
1.6G -rw-rw-r-- 1 summer 100G Apr 8 16:31 big.img
16:32 [summer@(protected) ~]$

ext3 happens about as quickly.

If you think that improbably fast, try on your own hardware.


> them but you can get journal aborts and remounting the FS read-only
> under heavier disk load in the guest! Use them only for testing purposes
> and/or when you are really low on space.

I don't see why a disk image should be any less reliable than any other
kind of file, catastrophic system failures (I'm thinking power and host
crashes) aside.



>
> Daniel
>
>
>
>  _____
>
> From: rhelv5-list-bounces@(protected)
> [mailto:rhelv5-list-bounces@(protected)
> Sent: Monday, April 07, 2008 5:38 PM
> To: Red Hat Enterprise Linux 5 (Tikanga) discussion mailing-list
> Subject: [rhelv5-list] Xen Guest Disk Formatting Unfeasibly Slow
>
>
> 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.
>
>
>
> ------------------------------------------------------------------------
>
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--

Cheers
John

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