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xen-users
Re: [Xen-users] File system layout
On Mon, 17 Mar 2008, Fajar A. Nugraha wrote:
Mark Williamson wrote:
My supervisor wants to create a LV then give that to a VM and then
create a VG with LV's under it inside the VM. I have read on the list
where this will give bad performance inside the VM.
It won't necessarily give *bad* performance but doing the two layers of
translation is a bit unfortunate.
An email from Sadique on this list sometime early this year said LVM has 2%
performance hit over pysical partitions. So using LVM on both dom0 and domU
(roughly) reduce performance by 4%.
To me, the simplicity of doing all LVM management in dom0 and hiding it
from the guest appeals.
It's actually possible to pass separate LVM volumes to appear as individual
partitions in the guest - this has the advantage that there's no MS-DOS
partition table to worry about, just a load of linear LVs with filesystems
on.
I second that. That is what we do for Linux PV guests.
For interest, how do you do this?
I can see how you can make dom0 lvs appear to the pv guest as separate
disks, and mke2fs each as a whole-disk file-system (without a
partition table.) But is there some trick to make separate dom0 lvs
appear to the domu guest as partitions on a single disk? If so, where
is the partition table, and where does grub install to?
Or, assuming separate disks, where does /boot go?
Do you make a small (100M) lv for /boot?
and how do you tell grub to boot from it - I tried it, and grub does not
seem able to install itself correctly - I get:
[root@domu ~ 0]$ grub-install /dev/hda
Unknown partition table signature
Unknown partition table signature
Unknown partition table signature
Unknown partition table signature
Unknown partition table signature
The file /boot/grub/stage1 not read correctly.
[root@domu ~ 1]$
Am I missing something obvious?
(using Centos 5.1 x86_64 as dom0 and domu)
Regards,
Fajar
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