[Gluster-users] gluster volume snap shot - basic questions

Rajesh Joseph rjoseph at redhat.com
Thu Sep 3 11:21:47 UTC 2015 


----- Original Message -----
> From: "Merlin Morgenstern" <merlin.morgenstern at gmail.com>
> To: "Rajesh Joseph" <rjoseph at redhat.com>
> Cc: "gluster-users" <gluster-users at gluster.org>
> Sent: Wednesday, September 2, 2015 8:27:40 PM
> Subject: Re: [Gluster-users] gluster volume snap shot - basic questions
> 
> Just double checked for the location of the snapshot files.
> 
> Documentations says they should be here:
> 
> A directory named snap will be created under the vol directory
> (..../glusterd/vols/<volname>/snap). Under which each created snap
> will be a self contained directory with meta files, and snap volumes
> 
> http://www.gluster.org/community/documentation/index.php/Features/snapshot
> 

The above link is little out-dated. Checkout the following links
http://www.gluster.org/community/documentation/index.php/Features/Gluster_Volume_Snapshot
http://rajesh-joseph.blogspot.in/p/gluster-volume-snapshot-howto.html

> Unfortunatelly they are not, they are in /var/lib/glusterd/snaps/
> 
> Each snap has a directory with volumes inside.
> 

Snapshot of a Gluster volume creates point-in-time copy of the entire volume. That's why
the snapshot of a Gluster volume is kind of a Gluster volume. As any regular Gluster Volume
snapshot also has data and volume config files associated with it.

The config files for snapshot is stored at /var/lib/glusterd/snaps/<snapname> directory.
The actual data (bricks) is stored in individual LVMs which are mounted at /var/run/gluster/snaps/<snap-volname>/brick<no>/


> If I want to use the dd command, which volume should I backup?
> 

I think this would be very primitive way of backup and might take lot of time doing actual backup.
Consider using some open-source backup solutions, e.g. Bareos, etc.

If you want to use dd then I suggest to mount the snapshot volume and then do dd on the mount point. Else
you need to take backup all bricks separately and handle replicas as well.

> ls:
> 
> node1:/data/mysql/data$ ll
> /var/lib/glusterd/snaps/snap1/2d828e6282964e0e89616b297130aa1b/
> 
> total 56
> 
> drwxr-xr-x 3 root root 4096 Sep  2 16:04 *.*/
> 
> drwxr-xr-x 4 root root 4096 Sep  2 16:04 *..*/
> 
> -rw------- 1 root root 4559 Sep  2 16:03
> 2d828e6282964e0e89616b297130aa1b.gs1.run-gluster-snaps-2d828e6282964e0e89616b297130aa1b-brick1-brick1.vol
> 
> -rw------- 1 root root 4559 Sep  2 16:03
> 2d828e6282964e0e89616b297130aa1b.gs2.run-gluster-snaps-2d828e6282964e0e89616b297130aa1b-brick2-brick1.vol
> 
> -rw------- 1 root root 2250 Sep  2 16:03
> 2d828e6282964e0e89616b297130aa1b-rebalance.vol
> 
> -rw------- 1 root root 2250 Sep  2 16:03
> 2d828e6282964e0e89616b297130aa1b.tcp-fuse.vol
> 
> drwxr-xr-x 2 root root 4096 Sep  2 16:04 *bricks*/
> 
> -rw------- 1 root root   16 Sep  2 16:04 cksum
> 
> -rw------- 1 root root  587 Sep  2 16:04 info
> 
> -rw------- 1 root root   93 Sep  2 16:04 node_state.info
> 
> -rw------- 1 root root    0 Sep  2 16:03 quota.conf
> 
> -rw------- 1 root root   13 Sep  2 16:04 snapd.info
> 
> -rw------- 1 root root 2478 Sep  2 16:03
> trusted-2d828e6282964e0e89616b297130aa1b.tcp-fuse.vol
> 
> 
> 
> 2015-09-02 16:31 GMT+02:00 Merlin Morgenstern <merlin.morgenstern at gmail.com>
> :
> 
> > So what would be the fastest possible way to make a backup to one single
> > fileof the entire file system? Would this be probably dd?
> >
> > e.g.:
> > sudo umount /run/gluster/snaps/7cb4b2c8f8a64ceaba62bc4ca6cd76b2/brick1
> >
> > sudo dd if=/dev/mapper/gluster-506cb09085b2428e9daca8ac0857c2c9_0 | gzip
> > > snap01.gz
> >
> > That seems to work, but how could I possibly know the snapshot name? I
> > took this info here from df -h since the snapshot can not be found under
> > /snaps/snapshot_name
> >
> > I also tried to run the command you mentioned:
> >
> > > to mount snapshot volume:
> > > mount -t glusterfs <hostname>:/snaps/<snap-name>/<origin-volname>
> > /<mount_point>
> >
> > This did not work. There seems not to be any folder called /snaps/ as when
> > I press tab I get suggestion for vol1 but nothing else.
> >
> > Here is the mount log:
> >
> > E [MSGID: 114058] [client-handshake.c:1524:client_query_portmap_cbk]
> > 0-vol1-client-0: failed to get the port number for remote subvolume. Please
> > run 'gluster volume status' on server to see if brick process is running.

By default snapshots are in deactivated state. You must activate them before mounting.
Use the following command to do so.

gluster snapshot activate <snapname>

or use the following config command to activate the snapshot by default.
gluster snapshot config activate-on-create enable

After the above command all the newly created snapshot will be activated by default.

> >
> > Thank you in advance for any help
> >
> >
> >
> > 2015-09-02 14:11 GMT+02:00 Rajesh Joseph <rjoseph at redhat.com>:
> >
> >>
> >>
> >> ----- Original Message -----
> >> > From: "Merlin Morgenstern" <merlin.morgenstern at gmail.com>
> >> > To: "Rajesh Joseph" <rjoseph at redhat.com>
> >> > Cc: "gluster-users" <gluster-users at gluster.org>
> >> > Sent: Wednesday, September 2, 2015 11:53:05 AM
> >> > Subject: Re: [Gluster-users] gluster volume snap shot - basic questions
> >> >
> >> > Thank you Rjesh for your help. I have a thinly provisioned LVM now
> >> running
> >> > and can create snapshots on a real device, surviving boot.
> >> >
> >> > There are 2 other questions rising up now.
> >> >
> >> > 1. I have a LV with 20G, data is 7G. How is it possible, that I could
> >> make
> >> > 3 snapshots, each 7G?
> >> >
> >> > /dev/mapper/gluster-thinv1                               20G  7.0G   12G
> >> > 38% /bricks/brick1
> >> >
> >> > /dev/mapper/gluster-7cb4b2c8f8a64ceaba62bc4ca6cd76b2_0   20G  7.0G   12G
> >> > 38% /run/gluster/snaps/7cb4b2c8f8a64ceaba62bc4ca6cd76b2/brick1
> >> >
> >> > /dev/mapper/gluster-506cb09085b2428e9daca8ac0857c2c9_0   20G  7.0G   12G
> >> > 38% /run/gluster/snaps/506cb09085b2428e9daca8ac0857c2c9/brick1
> >> >
> >> > /dev/mapper/gluster-fbee900c1cc7407f9527f98206e6566d_0   20G  7.0G   12G
> >> > 38% /run/gluster/snaps/fbee900c1cc7407f9527f98206e6566d/brick1
> >> >
> >> > /dev/mapper/gluster-d0c254908dca451d8f566be77437c538_0   20G  7.0G   12G
> >> > 38% /run/gluster/snaps/d0c254908dca451d8f566be77437c538/brick1
> >> >
> >> >
> >>
> >> These snapshots are copy-on-write (COW) therefore they hardly consume any
> >> space.
> >> As your main volume change the space consumption of the snapshots also
> >> grow.
> >> Check the "lvs" command to see the actual snapshot space consumption.
> >>
> >> You can get more detailed information if you search for thinly
> >> provisioned LVM and snapshots.
> >>
> >>
> >> > 2. The name of the snapshot folder is the UUID, My plan is to do a "tar
> >> cf"
> >> > on the snapshot and even incremental tars. Therefore I would need the
> >> name
> >> > of the folder. How could I pass that name to my bash script in order to
> >> > make a backup of the last snap?
> >> >
> >>
> >> Instead of taking per brick backup you can think of taking backup of the
> >> entire snapshot
> >> volume. You can mount the snapshot volume and perform the backup. Use the
> >> following command
> >> to mount snapshot volume:
> >> mount -t glusterfs <hostname>:/snaps/<snap-name>/<origin-volname>
> >> /<mount_point>
> >>
> >> or else if you want to find the name of the snapshot volume (UUID) then
> >> run the
> >> following command
> >> gluster snapshot info
> >>
> >> >
> >> > 3. A tar process will take hours on the million files I have. I
> >> understand
> >> > this is a snapshot, is there a way to backup a "single" snapshot file
> >> > instead?
> >>
> >> Snapshot is maintained in the underlying file-system and I see no way of
> >> transferring
> >> it to another system.
> >>
> >> >
> >> > Thank you in advance for sheding some light on this topic
> >> >
> >> > 2015-09-02 7:59 GMT+02:00 Rajesh Joseph <rjoseph at redhat.com>:
> >> >
> >> > >
> >> > >
> >> > > ----- Original Message -----
> >> > > > From: "Merlin Morgenstern" <merlin.morgenstern at gmail.com>
> >> > > > To: "gluster-users" <gluster-users at gluster.org>
> >> > > > Sent: Tuesday, September 1, 2015 3:15:43 PM
> >> > > > Subject: [Gluster-users] gluster volume snap shot - basic questions
> >> > > >
> >> > > > Hi everybody,
> >> > > >
> >> > > > I am looking into the snap shot tool, following this tutorial:
> >> > > > http://blog.gluster.org/2014/10/gluster-volume-snapshot-howto/
> >> > > >
> >> > > > While having successfully created the LVM, gluster volume and one
> >> > > snapshot,
> >> > > > there are some questions arrising where I was hoping to find some
> >> > > guidence
> >> > > > here:
> >> > > >
> >> > > > 1. From a working setup as in the example I rebooted and everything
> >> was
> >> > > gone.
> >> > > > How can I make this setup persistent, so the gluster share is up and
> >> > > running
> >> > > > after boot.
> >> > > >
> >> > >
> >> > > What do you mean by "everything was gone"? Are you using loop back
> >> device
> >> > > as disks?
> >> > > If yes then this is expected. Loop back device mapping is gone after
> >> > > machine restart.
> >> > > You should test with real disk or lvm partition.
> >> > >
> >> > > > 2. I understand that the snaps are under /var/run/gluster/snaps/
> >> and I
> >> > > found
> >> > > > them there. Is it save to simply copy them to another server for
> >> backup?
> >> > > My
> >> > > > goal is to create a backup each day and transfer the snaps to an
> >> > > FTP-Server
> >> > > > in order to be able to recover from a broken machine.
> >> > > >
> >> > >
> >> > > Yes, snap of individual bricks are mounted at
> >> /var/run/gluster/snaps/. I
> >> > > am assuming
> >> > > that you mean copy of data hosted on the snap brick when you say copy
> >> the
> >> > > snap.
> >> > > Are you planning to use some backup software or to run rsync on each
> >> brick?
> >> > >
> >> > > > 3. Do I really need LVM to use this feature? Currently my setup
> >> works on
> >> > > the
> >> > > > native system. As I understand the tuturial I would need to move
> >> that to
> >> > > a
> >> > > > LV, right?
> >> > > >
> >> > >
> >> > > Yes, you need LVM and to be precise thinly provisioned LVM for
> >> snapshot to
> >> > > work.
> >> > >
> >> > > > Thank you in advance on any help!
> >> > > >
> >> > > > _______________________________________________
> >> > > > Gluster-users mailing list
> >> > > > Gluster-users at gluster.org
> >> > > > http://www.gluster.org/mailman/listinfo/gluster-users
> >> > >
> >> >
> >>
> >
> >
>

More information about the Gluster-users mailing list