I''m using xen 4.1.2 on fedora 16. I''m aware that it''s possible to snapshot vms using lvm snapshots but it''s a lengthier and more involved process than the type of one step snapshot functionality included in citrix xenserver or xcp. Therefore I wanted to ask: (i) does anyone know if it''s possible to create snapshots using the libvirt library e.g. virsh snapshot-create. I don''t believe it is but I wanted to check. When I try I get an error message saying: "error: this function is not supported by the connection driver: virDomainSnapshotCreateXML" (ii) putting lvm aside, are there any other snapshot options available for xen if one isn''t using xcp Thanks in advance for any help. _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
This isn't too helpful, but regarding (ii), dd if=/path/to/domU/partition/or/disk.img of=/path/to/drive/with/enough/space/to/store/a/copy.img bs=8M or the like should do the trick for your disk, and just make a copy of your domU config file. There's also xm snapshot-create, but I'm not too sure how well (or even how) that works. On Fri, Dec 30, 2011 at 6:58 PM, Adam Gold <adamgold@hotmail.com> wrote:> I'm using xen 4.1.2 on fedora 16. I'm aware that it's possible to snapshot > vms using lvm snapshots but it's a lengthier and more involved process than > the type of one step snapshot functionality included in citrix xenserver or > xcp. Therefore I wanted to ask: > > (i) does anyone know if it's possible to create snapshots using the libvirt > library e.g. virsh snapshot-create. I don't believe it is but I wanted to > check. When I try I get an error message saying: "error: this function is > not supported by the connection driver: virDomainSnapshotCreateXML" > (ii) putting lvm aside, are there any other snapshot options available for > xen if one isn't using xcp > > Thanks in advance for any help. > > _______________________________________________ > Xen-users mailing list > Xen-users@lists.xensource.com > http://lists.xensource.com/xen-users_______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
Thanks for the response. Yes, dd is one way of achieving what I want - which is to allow rollbacks to earlier states - but I guess, if one''s going to be slightly pedantic, it''s more a cloning solution than a snapshot (and at this point I could just go with lvm snapshots). It''s certainly a possibility but I am curious to know if there''s anything out there which mirrors the simplicity and speed of the snapshot functionality in XCP. I''m guessing not yet...> From: kyl191@kyl191.net > Date: Sat, 31 Dec 2011 16:04:05 +0800 > Subject: Re: [Xen-users] snapshots (without lvm) > To: adamgold@hotmail.com > CC: xen-users@lists.xensource.com > > This isn''t too helpful, but regarding (ii), dd > if=/path/to/domU/partition/or/disk.img > of=/path/to/drive/with/enough/space/to/store/a/copy.img bs=8M or the > like should do the trick for your disk, and just make a copy of your > domU config file. > > There''s also xm snapshot-create, but I''m not too sure how well (or > even how) that works. > > On Fri, Dec 30, 2011 at 6:58 PM, Adam Gold <adamgold@hotmail.com> wrote: > > I''m using xen 4.1.2 on fedora 16. I''m aware that it''s possible to snapshot > > vms using lvm snapshots but it''s a lengthier and more involved process than > > the type of one step snapshot functionality included in citrix xenserver or > > xcp. Therefore I wanted to ask: > > > > (i) does anyone know if it''s possible to create snapshots using the libvirt > > library e.g. virsh snapshot-create. I don''t believe it is but I wanted to > > check. When I try I get an error message saying: "error: this function is > > not supported by the connection driver: virDomainSnapshotCreateXML" > > (ii) putting lvm aside, are there any other snapshot options available for > > xen if one isn''t using xcp > > > > Thanks in advance for any help. > > > > _______________________________________________ > > Xen-users mailing list > > Xen-users@lists.xensource.com > > http://lists.xensource.com/xen-users_______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users
> Thanks for the response. Yes, dd is one way of achieving what I want > - which is to allow rollbacks to earlier states - but I guess, if > one''s going to be slightly pedantic, it''s more a cloning solution > than a snapshot (and at this point I could just go with lvm > snapshots). It''s certainly a possibility but I am curious to know if > there''s anything out there which mirrors the simplicity and speed of > the snapshot functionality in XCP. I''m guessing not yet...Maybe I''m not answering your question in the way you''d like it to be answered, but at least I can show you my two snapshot/backup methods. For images that I want to store on dom0 I prefer the following method: # kpartx -a /dev/vg/lv-domu # mount -o ro /dev/mapper/vg-lv-domu3 /mnt (mount filesystem root) # mount -o ro /dev/mapper/vg-lv-domu1 /mnt/boot # cd /var/snapshots/domu # rsync -aPh --delete --delete-excluded /mnt . # umount, kpartx -d ... etc. Usually I make a tar file out of this with some compression... lzop is nice here because it''s very fast and still provides a reasonable amount of compression. This is how I prefer to make a snapshot of a newly installed system. Besides this I also want to make incremental backups of systems that are already configured and running. For this I use rsnapshot on a dedicated backup system which is separate from the Xen box which is what I''ll explain next. All the domU''s initiate an openvpn connection to the rsnapshot system. The rsnapshot / openvpn server assigns these hosts an IPv6 ULA (Unique Local Address) because these address forms are unroutable on the Internet and thus are considered safe enough for this purpose. The domU''s also all have an rsync daemon that listens to only this address. Rsyncd provides read-only access to the whole filesystem (/) for only the rsnapshot system''s IPv6 ULA address. The rsnapshot system connects to the domU''s four times a day and makes incremental backups each time. This means that files that already exist on the rsnapshot system are linked rather than duplicated and retransferred - this saves a lot of space and bandwidth and increases speed. The exclusion of files and directories is configured in rsnapshot''s config file. Rsnapshot also makes daily, weekly and monthly snapshots but this happens locally i.e. without making connections to the backuped boxes. I chose rsyncd rather than ssh because there is no mandatory authentication, it simply allows only the rsnapshot system''s IP. Furthermore OpenVPN already establishes the encrypted connection and I see no reason to make the encryption redundant (i.e. encrypted ssh over encrypted OpenVPN). And rsyncd also is a lot faster than ssh. Those who would rather use rsnapshot over ssh than over an OpenVPN connection could choose to use ssh with the arcfour cipher because arcfour is a faster streaming cipher than the other ones. I hope I explained it in an understandable way but if you prefer a less theoretical and more practical explanation then just say so. I''ll then write something that shows you the used commands and config files. -Mark
Thanks Mark. That''s very clear and seems like a sensible approach (I like the use of openvpn). I''d be interested to hear how you go about making restores when needed, and specifically a full system restore/rollback. If one is making file based/tar backups as you are, it''s never been clear to me how to achieve a ''perfect'' full disk/full partition restore in the way one can do with dd or a third party solution like clonezilla. That''s why I like the simplicity of the true snapshot or cloning approach to implement system rollbacks. However, it may well be I''m missing something when it comes to how rsnapshot works so: (i) Yes, I''d love to hear more about the config and particular commands (ii) please do tell me more about how the restoring side of the equation works e.g. let''s say you wanted to revert one of your domUs from incremental version 4 on a particular day to version 1 (and to be clear, not specific files but the whole system), how would that work? How do you deal with excluded directories (proc,sys etc) during the restore process. Thanks. P.S. I agree, lzop is the best compression algorithm for this type of work. Date: Sat, 31 Dec 2011 13:15:11 +0100 From: Mark van Dijk <mark@internecto.net> To: xen-users@lists.xensource.com Subject: Re: [Xen-users] snapshots (without lvm) Message-ID: <20111231121553.306572988E4@mx1.internecto.net> Content-Type: text/plain; charset=US-ASCII> Thanks for the response. Yes, dd is one way of achieving what I want > - which is to allow rollbacks to earlier states - but I guess, if > one''s going to be slightly pedantic, it''s more a cloning solution > than a snapshot (and at this point I could just go with lvm > snapshots). It''s certainly a possibility but I am curious to know if > there''s anything out there which mirrors the simplicity and speed of > the snapshot functionality in XCP. I''m guessing not yet...Maybe I''m not answering your question in the way you''d like it to be answered, but at least I can show you my two snapshot/backup methods. For images that I want to store on dom0 I prefer the following method: # kpartx -a /dev/vg/lv-domu # mount -o ro /dev/mapper/vg-lv-domu3 /mnt (mount filesystem root) # mount -o ro /dev/mapper/vg-lv-domu1 /mnt/boot # cd /var/snapshots/domu # rsync -aPh --delete --delete-excluded /mnt . # umount, kpartx -d ... etc. Usually I make a tar file out of this with some compression... lzop is nice here because it''s very fast and still provides a reasonable amount of compression. This is how I prefer to make a snapshot of a newly installed system. Besides this I also want to make incremental backups of systems that are already configured and running. For this I use rsnapshot on a dedicated backup system which is separate from the Xen box which is what I''ll explain next. All the domU''s initiate an openvpn connection to the rsnapshot system. The rsnapshot / openvpn server assigns these hosts an IPv6 ULA (Unique Local Address) because these address forms are unroutable on the Internet and thus are considered safe enough for this purpose. The domU''s also all have an rsync daemon that listens to only this address. Rsyncd provides read-only access to the whole filesystem (/) for only the rsnapshot system''s IPv6 ULA address. The rsnapshot system connects to the domU''s four times a day and makes incremental backups each time. This means that files that already exist on the rsnapshot system are linked rather than duplicated and retransferred - this saves a lot of space and bandwidth and increases speed. The exclusion of files and directories is configured in rsnapshot''s config file. Rsnapshot also makes daily, weekly and monthly snapshots but this happens locally i.e. without making connections to the backuped boxes. I chose rsyncd rather than ssh because there is no mandatory authentication, it simply allows only the rsnapshot system''s IP. Furthermore OpenVPN already establishes the encrypted connection and I see no reason to make the encryption redundant (i.e. encrypted ssh over encrypted OpenVPN). And rsyncd also is a lot faster than ssh. Those who would rather use rsnapshot over ssh than over an OpenVPN connection could choose to use ssh with the arcfour cipher because arcfour is a faster streaming cipher than the other ones. I hope I explained it in an understandable way but if you prefer a less theoretical and more practical explanation then just say so. I''ll then write something that shows you the used commands and config files. -Mark