Re: [Xen-users] Ubuntu HVM installation is very slow

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

On Tue, May 19, 2009 at 7:28 PM, Dot Yet <dot.yet@xxxxxxxxx> wrote:
> I am trying my hands on xen under Solaris SXCE build 113.

You might find more SXCE/opensolaris users, as well as Sun's
developers on xen-discuss@xxxxxxxxxxxxxxx

> The problem is that xen HVM is very slow. I am using the following command
> to create an Ubuntu 9.0.4 test vm.
>
> virt-install -n test1 -r 2048 --vcpus=2 -f /vdatapool/data/test1.img -s 50
> --vnc --hvm  --os-type=linux --location=/vsafepool/shared/
> Installs/Linux/ubuntu-9.04-desktop-amd64.iso

file-based vbds tend to be slower compared to phy:/. Try using zvol
and see if it helps.
While we're at it, why HVM? Why not PV guest, which should provide
much better performance?

>
> Based on some random bits found on google, i did hear it to be slow, but did
> not expect it to be crawling slow.

Slow is relative :)
While it is MUCH slower compared to native or PV guest install, last
time I tested it's comparable to Windows HVM install. This is why IMHO
HVM guest is only usable with PV drivers. Meaning Ubuntu HVM install
will be almost useless for production purposes since AFAIK there's no
PV driver for its default kernel yet. I actually have an Ubuntu HVM
(for testing purposes) and I changed its kernel to RHEL 5.3's
kernel-xen (which has built in PV drivers). The performance
improvement was HUGE.



> Following is the output from zpool's iostat:
>
> vdatapool    79.8G   848G      0    135      0  17.0M

17MB/s write with 135 writes/s is a lot (well it can be a lot
depending on disk).
Try using iostat to see if the disk has maxed out its bandwidth or IOPS.

> some data from vmstat as well:

Try "xm top".

-- 
Fajar

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