This is an archived copy of the Xen.org mailing list, which we have preserved to ensure that existing links to archives are not broken. The live archive, which contains the latest emails, can be found at http://lists.xen.org/
Home Products Support Community News


Re: [Xen-users] very slow disk access

On 2/27/2011 2:25 AM, Fajar A. Nugraha wrote:
On Sun, Feb 27, 2011 at 9:11 AM, Randy Katz<rkatz@xxxxxxxxxxxxxxxxxxxxx>  wrote:
it seems I am using tap:aio on what appears to be quite slow:

disk = [ "tap:aio:/disk0/server3.img,xvda,w" ]

Is there a good way to convert from tap:aio to lvm? I tried stop vm, dd
if=server3.img of=/dev/vg1/newlv3
but it is very very slow, much quicker to blow away the whole thing (vm) and
reinstall and then add data
from backups.
dd is the generic way. You might want to use dd_rescue (available as
rpm from EPEL), which should at least show you what it's doing and how
fast it's doing it. 6 - 10MBps is quite normal if you only have one

If your image is still empty-ish (e.g 20GB file image with only 2GB
used), it might be faster to copy MBR first (which includes partition
table), setup your system so you could access the partition on LVM
(using something like kpartx), and use something like partclone or
clone2fs to copy only used blocks.

Cool stuff Fajar, thank you much!


Xen-users mailing list

<Prev in Thread] Current Thread [Next in Thread>