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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] RE: [Xen-users] Xen 4.0 feature request
The fact of the matter is that without flushing the buffers and cache, the snapshot is essentially the same as what would result if you pulled the power plug (sans the messy 'memory death' results that happen in the physical world in the nanoseconds after RAM loses power) -and while that's hardly ideal, it's good enough for many purposes - databases and filesystems are generally robust enough to handle uncommitted transactions. However, there are ways to get a better snapshot. All you need is a quick script that logs in to the domU, stops the database service, runs a sync, and then generates the snapshot and starts the database service again. Best Regards Nathan Eisenberg Sr. Systems Administrator Atlas Networks, LLC support@xxxxxxxxxxxxxxxx http://support.atlasnetworks.us/portal -----Original Message----- From: xen-users-bounces@xxxxxxxxxxxxxxxxxxx [mailto:xen-users-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Simon Hobson Sent: Monday, July 06, 2009 11:26 AM To: xen-users@xxxxxxxxxxxxxxxxxxx Subject: RE: [Xen-users] Xen 4.0 feature request Nathan Eisenberg wrote: >Why can't you save only one VM with LVM snapshots? Sounds like you >have an odd implementation, rather that there being a problem with >LVM. We export two LVs per domU - 1 'data' and 1 'swap'. I can >easily snapshot the 'data' LV of any single domU without a >performance problem. How do you deal with the fact that you are snapshotting a dirty state ? Unless you are using LVM inside the DomU (in which case Xen is irrelevant), then when you make a snapshot, it will NOT include any dirty blocks in the guests cache. Unless you collaborate with the guest, get it to stop updating the filesystem, and flush it's cache - then you are pretty well guaranteed dirty (and probably corrupt) data. -- 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@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-users _______________________________________________ Xen-users mailing list Xen-users@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-users
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