On Mon, Jul 9, 2018 at 5:41 PM, Hesham Ahmed <hsahmed(a)gmail.com> wrote:
>
> Thanks Sahina for the update,
>
> I am using gluster geo-replication for DR in a different installation,
> however I was not aware that Gluster snapshots are not recommended in
> a hyperconverged setup, don't. A warning on the Gluster snapshot UI
> would be helpful. Is gluster volume snapshots for volumes hosting VM
> images a work in progress with a bug tracker or it's something not
> expected to change?
Agreed on the warning - can you log a bz?
There's no specific bz tracking support for volume snapshots w.r.t VM store use case.
If you have a specific scenario where the geo-rep based DR is not sufficient, please log a
bug.
> On Mon, Jul 9, 2018 at 2:58 PM Sahina Bose <sabose(a)redhat.com> wrote:
> >
> >
> >
> > On Sun, Jul 8, 2018 at 3:29 PM, Hesham Ahmed <hsahmed(a)gmail.com> wrote:
> >>
> >> I also noticed that Gluster Snapshots have the SAME UUID as the main
> >> LV and if using UUID in fstab, the snapshot device is sometimes
> >> mounted instead of the primary LV
> >>
> >> For instance:
> >> /etc/fstab contains the following line:
> >>
> >> UUID=a0b85d33-7150-448a-9a70-6391750b90ad /gluster_bricks/gv01_data01
> >> auto
inode64,noatime,nodiratime,x-parent=dMeNGb-34lY-wFVL-WF42-hlpE-TteI-lMhvvt
> >> 0 0
> >>
> >> # lvdisplay gluster00/lv01_data01
> >> --- Logical volume ---
> >> LV Path /dev/gluster00/lv01_data01
> >> LV Name lv01_data01
> >> VG Name gluster00
> >>
> >> # mount
> >> /dev/mapper/gluster00-55e97e7412bf48db99bb389bb708edb8_0 on
> >> /gluster_bricks/gv01_data01 type xfs
> >>
(rw,noatime,nodiratime,seclabel,attr2,inode64,sunit=1024,swidth=2048,noquota)
> >>
> >> Notice above the device mounted at the brick mountpoint is not
> >> /dev/gluster00/lv01_data01 and instead is one of the snapshot devices
> >> of that LV
> >>
> >> # blkid
> >> /dev/mapper/gluster00-lv01_shaker_com_sa:
> >> UUID="a0b85d33-7150-448a-9a70-6391750b90ad" TYPE="xfs"
> >> /dev/mapper/gluster00-55e97e7412bf48db99bb389bb708edb8_0:
> >> UUID="a0b85d33-7150-448a-9a70-6391750b90ad" TYPE="xfs"
> >> /dev/mapper/gluster00-4ca8eef409ec4932828279efb91339de_0:
> >> UUID="a0b85d33-7150-448a-9a70-6391750b90ad" TYPE="xfs"
> >> /dev/mapper/gluster00-59992b6c14644f13b5531a054d2aa75c_0:
> >> UUID="a0b85d33-7150-448a-9a70-6391750b90ad" TYPE="xfs"
> >> /dev/mapper/gluster00-362b50c994b04284b1664b2e2eb49d09_0:
> >> UUID="a0b85d33-7150-448a-9a70-6391750b90ad" TYPE="xfs"
> >> /dev/mapper/gluster00-0b3cc414f4cb4cddb6e81f162cdb7efe_0:
> >> UUID="a0b85d33-7150-448a-9a70-6391750b90ad" TYPE="xfs"
> >> /dev/mapper/gluster00-da98ce5efda549039cf45a18e4eacbaf_0:
> >> UUID="a0b85d33-7150-448a-9a70-6391750b90ad" TYPE="xfs"
> >> /dev/mapper/gluster00-4ea5cce4be704dd7b29986ae6698a666_0:
> >> UUID="a0b85d33-7150-448a-9a70-6391750b90ad" TYPE="xfs"
> >>
> >> Notice the UUID of LV and its snapshots is the same causing systemd to
> >> mount one of the snapshot devices instead of LV which results in the
> >> following gluster error:
> >>
> >> gluster> volume start gv01_data01 force
> >> volume start: gv01_data01: failed: Volume id mismatch for brick
> >> vhost03:/gluster_bricks/gv01_data01/gv. Expected volume id
> >> be6bc69b-c6ed-4329-b300-3b9044f375e1, volume id
> >> 55e97e74-12bf-48db-99bb-389bb708edb8 found
> >
> >
> >
> > We do not recommend gluster volume snapshots for volumes hosting VM images.
Please look at the
https://ovirt.org/develop/release-management/features/gluster/gluster-dr/ as an
alternative.
> >
> >>
> >> On Sun, Jul 8, 2018 at 12:32 PM <hsahmed(a)gmail.com> wrote:
> >> >
> >> > I am facing this trouble since version 4.1 up to the latest 4.2.4,
once
> >> > we enable gluster snapshots and accumulate some snapshots (as few as
15
> >> > snapshots per server) we start having trouble booting the server. The
> >> > server enters emergency shell upon boot after timing out waiting for
> >> > snapshot devices. Waiting a few minutes and pressing Control-D then
boots the server normally. In case of very large number of snapshots (600+) it can take
days before the sever will boot. Attaching journal
> >> > log, let me know if you need any other logs.
> >> >
> >> > Details of the setup:
> >> >
> >> > 3 node hyperconverged oVirt setup (64GB RAM, 8-Core E5 Xeon)
> >> > oVirt 4.2.4
> >> > oVirt Node 4.2.4
> >> > 10Gb Interface
> >> >
> >> > Thanks,
> >> >
> >> > Hesham S. Ahmed
> >
> >
We were not using gluster snapshots for DR rather as a quick way to go
back in time (although we never planned how to use the snapshots).
Maybe scheduling ability should be added for VM snapshots as well.