On Tue, Feb 27, 2018 at 1:40 PM, Dave Sherohman <dave@xxxxxxxxxxxxx> wrote:
[1] http://docs.gluster.org/en/latest/Administrator%20Guide/arbiter-volumes-and-quorum/#arbiter-bricks-sizing
Regards,
On Tue, Feb 27, 2018 at 12:00:29PM +0530, Karthik Subrahmanya wrote:
> I will try to explain how you can end up in split-brain even with cluster
> wide quorum:
Yep, the explanation made sense. I hadn't considered the possibility of
alternating outages. Thanks!
> > > It would be great if you can consider configuring an arbiter or
> > > replica 3 volume.
> >
> > I can. My bricks are 2x850G and 4x11T, so I can repurpose the small
> > bricks as arbiters with minimal effect on capacity. What would be the
> > sequence of commands needed to:
> >
> > 1) Move all data off of bricks 1 & 2
> > 2) Remove that replica from the cluster
> > 3) Re-add those two bricks as arbiters
> >
> > (And did I miss any additional steps?)
> >
> > Unfortunately, I've been running a few months already with the current
> > configuration and there are several virtual machines running off the
> > existing volume, so I'll need to reconfigure it online if possible.
> >
> Without knowing the volume configuration it is difficult to suggest the
> configuration change,
> and since it is a live system you may end up in data unavailability or data
> loss.
> Can you give the output of "gluster volume info <volname>"
> and which brick is of what size.
Volume Name: palantir
Type: Distributed-Replicate
Volume ID: 48379a50-3210-41b4-9a77-ae143c8bcac0
Status: Started
Snapshot Count: 0
Number of Bricks: 3 x 2 = 6
Transport-type: tcp
Bricks:
Brick1: saruman:/var/local/brick0/data
Brick2: gandalf:/var/local/brick0/data
Brick3: azathoth:/var/local/brick0/data
Brick4: yog-sothoth:/var/local/brick0/data
Brick5: cthulhu:/var/local/brick0/data
Brick6: mordiggian:/var/local/brick0/data
Options Reconfigured:
features.scrub: Inactive
features.bitrot: off
transport.address-family: inet
performance.readdir-ahead: on
nfs.disable: on
network.ping-timeout: 1013
performance.quick-read: off
performance.read-ahead: off
performance.io-cache: off
performance.stat-prefetch: off
cluster.eager-lock: enable
network.remote-dio: enable
cluster.quorum-type: auto
cluster.server-quorum-type: server
features.shard: on
cluster.data-self-heal-algorithm: full
storage.owner-uid: 64055
storage.owner-gid: 64055
For brick sizes, saruman/gandalf have
$ df -h /var/local/brick0
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/gandalf-gluster 885G 55G 786G 7% /var/local/brick0
and the other four have
$ df -h /var/local/brick0
Filesystem Size Used Avail Use% Mounted on
/dev/sdb1 11T 254G 11T 3% /var/local/brick0
If you want to use the first two bricks as arbiter, then you need to be aware of the following things:
- Your distribution count will be decreased to 2.
- Your data on the first subvol i.e., replica subvol - 1 will be unavailable till it is copied to the other subvols
after removing the bricks from the cluster.
Since arbiter bricks need not be of same size as the data bricks, if you can configure three more arbiter bricks
based on the guidelines in the doc [1], you can do it live and you will have the distribution count also unchanged.
based on the guidelines in the doc [1], you can do it live and you will have the distribution count also unchanged.
One more thing from the volume info; Only the options which are reconfigured will appear in the volume info output.
The quorum-type is in the list which says it is manually reconfigured.
The quorum-type is in the list which says it is manually reconfigured.
[1] http://docs.gluster.org/en/latest/Administrator%20Guide/arbiter-volumes-and-quorum/#arbiter-bricks-sizing
Regards,
Karthik
--
Dave Sherohman
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