I had used dd to copy vm to hard drive . Once freenas runs on xen again i am thinking about exporting iscsi and using dd to make copies _______________________________________________ Xen-users mailing list Xen-users@lists.xen.org http://lists.xen.org/xen-users
On Apr 18, 2013 4:20 PM, "jacek burghardt" <jaceksburghardt@gmail.com> wrote:> > I had used dd to copy vm to hard drive . Once freenas runs on xen again iam thinking about exporting iscsi and using dd to make copies> >Beware! Using dd to do online backups is just begging for trouble. Unless no files are written during the entire backup, there is NO guarantee of consistency. dd is for offline backups only. _______________________________________________> Xen-users mailing list > Xen-users@lists.xen.org > http://lists.xen.org/xen-users_______________________________________________ Xen-users mailing list Xen-users@lists.xen.org http://lists.xen.org/xen-users
If you do a dd of an lvm snapshot, doesn''t that promise that no writes were taking place during that time? However I know that this type of backup is identical to pulling out the power, which might not be to bad in some circumstances depending on applications running and the volatility of the data, but is generally frowned upon. On Thu, Apr 18, 2013 at 4:44 PM, Sean Greenslade <zootboysean@gmail.com>wrote:> > On Apr 18, 2013 4:20 PM, "jacek burghardt" <jaceksburghardt@gmail.com> > wrote: > > > > I had used dd to copy vm to hard drive . Once freenas runs on xen again > i am thinking about exporting iscsi and using dd to make copies > > > > > > Beware! Using dd to do online backups is just begging for trouble. Unless > no files are written during the entire backup, there is NO guarantee of > consistency. dd is for offline backups only. > _______________________________________________ > > Xen-users mailing list > > Xen-users@lists.xen.org > > http://lists.xen.org/xen-users > > _______________________________________________ > Xen-users mailing list > Xen-users@lists.xen.org > http://lists.xen.org/xen-users >_______________________________________________ Xen-users mailing list Xen-users@lists.xen.org http://lists.xen.org/xen-users
(Try to avoid top-posting) On Thu, Apr 18, 2013 at 4:57 PM, Andrew Wells <agwells0714@gmail.com> wrote:> If you do a dd of an lvm snapshot, doesn''t that promise that no writes were > taking place during that time? However I know that this type of backup is > identical to pulling out the power, which might not be to bad in some > circumstances depending on applications running and the volatility of the > data, but is generally frowned upon. >I must have missed the LVM snapshot bit. I was referring to doing a dd on a live, mounted partition (which is what I assumed the suggestion was for). Doing this is a bad idea, as any file edits that occur after the partition index sectors have been copied will leave the index out of sync with the data. Thus, any edit can potentially corrupt your backup. Now, if it''s an LVM snapshot that''s not currently in use, then a dd would be acceptable (though you may consider using something like partclone, which can intelligently copy and compress most filesystems). The other issue that you touch on is one that I don''t know enough about to answer. This post[1] leads me to believe that snapshots should be atomic, but I don''t know for sure. It seems like it would depend on your filesystem. I also found a little bit on doing [semi]automated LVM snapshots [2]. Maybe it will be of help. [1] http://stackoverflow.com/questions/1940093/lvm-snapshot-of-mounted-filesystem [2] http://tldp.org/HOWTO/LVM-HOWTO/snapshots_backup.html -- --Zootboy Sent from some sort of computing device.