Re: [Xen-users] Is LVM really that much slower than Container?

["Fajar A. Nugraha" <fajar@xxxxxxxxx>]

On Mon, Apr 13, 2009 at 7:05 PM, Tim Kaufmann <tim@xxxxxxxxxxxxxx> wrote:
>
> Am 13.04.2009 um 07:32 schrieb Fajar A. Nugraha:
>
>> Does dom0 uses more than 400MB
>> memory (try xm list)?
>
> Yes, it uses all the RAM which is not used by the domU.
>
>> It's not recommended to use file:/ as it's possible to cause data
>> corruption. Try changing it to tap:aio:/, and you should see that LVM
>> is faster.
>
> Unfortunately trying to boot domU1 from the container with tap:aio:/ totally
> locks up dom0 as the screen with the Windows Logo and the progress bar
> appears. It makes no difference whether I boot with /gplpv or not. The last
> entries from /var/log/syslog:

> Anyhow: If tap:aio:/ is supposed to be even slower than LVM, I fear all this
> might lead me nowhere. My trusty old server (P4@2,6GHz, 2 GB RAM, Ubuntu
> Hardy LTS, no RAID) runs XP on VirtualBox 2.1. The filecopy over the network
> takes 3 minutes (2 Minutes on domU2), creating a local copy 2 minutes (80
> seconds on domU2). Hope nobody's gonna kill me if I dare to ask where the
> performance gain I expected from the newer hardware and the Xen hypervisor
> went?

I missed the part in your earlier post saying that you use Ubuntu :)
If I remember correctly some version of Ubuntu (maybe it still does?)
have a bug in tap:aio. It's better to compile xen yourself.

Since your local copy operation is also slow, here's what I can tell you :
- I'm using Xen 3.3.1 on top of RHEL 5.3
- on dom0, ext3 on top of LVM :
# time (cp test400M test400M2;sync)

real    0m5.416s
user    0m0.068s
sys     0m0.984s

- on Windows domU + cygwin, GPLPV, on top of LVM
$ time ( cp test400M test400M2;sync )

real    0m14.320s
user    0m0.070s
sys     0m2.042s

"test400M" is a 400-MB zero-filled file created with dd. As you can
see my result is much faster compared to yours.

Try testing dom0 first, maybe your setup is somehow messed up (xen
problem, driver problem, etc.). If that's good, try on domU with
GPLPV.

Regards,

Fajar

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