mukul
2010-Aug-19 11:26 UTC
[Xen-users] Can I mount the xen image file while vm is running
Hi All I have a Two running VM''s Name ID Mem(MiB) VCPUs State Time(s) Domain-0 0 1306 2 r----- 940.1 vm101 1 216 1 -b---- 11.7 vm102 2 216 1 -b---- 11.9 both running CentOS release 5.5 If i mount one of the images manually while the machine is running will it make any differnce to the Running VM ? ? Regards Maddie _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Fajar A. Nugraha
2010-Aug-19 12:40 UTC
Re: [Xen-users] Can I mount the xen image file while vm is running
On Thu, Aug 19, 2010 at 6:26 PM, mukul <mkl1983@rediffmail.com> wrote:> If i mount one of the images manually while the machine is running will it make any differnce to the > Running VM ? ?That will most likely cause data corruption. You need something like LVM snapshot (if using phy:/ with LVM-backed storage) or use some storage-specific snapshot method (like vhd snapshot, which is not available on Centos 5.5: http://lxr.xensource.com/lxr/source/tools/blktap2/README). If you have snapshot (using whatever method), then you should be able to safely mount the snapshot on dom0, while domU continues to access the original storage. -- Fajar _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
maddie
2010-Aug-19 13:10 UTC
[Xen-users] Re: Can I mount the xen image file while vm is running
If i mounted the VM READ only then would the data getcorrupted ? ? ? -- View this message in context: http://xen.1045712.n5.nabble.com/Can-I-mount-the-xen-image-file-while-vm-is-running-tp2640786p2640887.html Sent from the Xen - User mailing list archive at Nabble.com. _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Fajar A. Nugraha
2010-Aug-19 13:18 UTC
Re: [Xen-users] Re: Can I mount the xen image file while vm is running
On Thu, Aug 19, 2010 at 8:10 PM, maddie <mkl1983@rediffmail.com> wrote:> > If i mounted the VM READ only then would the data getcorrupted ? ? ?DId you mean mount the filesystem read-only on dom0? Most modern filesystem (like ext3) requires replaying journal when mounting a "dirty" (i.e. not cleanly unmounted) filesystem. The journal replay process perform writes to the underlying device, thus can still cause corruption. -- Fajar _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Simon Hobson
2010-Aug-19 14:57 UTC
[Xen-users] Re: Can I mount the xen image file while vm is running
maddie wrote:>If i mounted the VM READ only then would the data getcorrupted ? ? ?But you need to remember that what is on the physical storage is **NOT** the contents of the file system (in general). The DomU will have unwritten changes help in ram - the contents of storage are as you would find after pulling the power plug ! Even if you sync the disk in DomU, then future changes would not be ''noticed'' by Dom0 - or rather they may or may not depending on what is currently cached in Dom0 and when it reads stuff from the disk relative to when the DomU writes it. Since most os''s will keep some key filesystem information in memory, it''s not likely that the version ''known'' to Dom0 will stay valid for long. -- Simon Hobson Visit http://www.magpiesnestpublishing.co.uk/ for books by acclaimed author Gladys Hobson. Novels - poetry - short stories - ideal as Christmas stocking fillers. Some available as e-books. _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users