[Gluster-users] Volume to store vm

Ramon Selga ramon.selga at gmail.com
Fri Sep 6 21:08:52 UTC 2019

Hi Cristian,

Both approaches are correct but they have different usable capacity and 
tolerance to node failures.

First one is a full replica 3 meaning you get your total node capacity divided 
by 3, because replica 3, and it tolerates a simultaneous of two nodes and very 
good for split-brain avoidance.

Second one is a replica 2 with arbiter, also very good for split-brain avoidance 
(that's purpose of arbiter bricks). In this case you get your total capacity 
divided by two except a little space going to arbiter-bricks, may be less than 
1% of normal storage bricks. It tolerates one node failure at the same time.

For VM usage remember to enable sharding with a shard size of 256MB at least 
before use volume.

If efficiency between total and usable capacity is a concern for you and you 
think you could tolerate only one node failure at the same time, may I suggest 
you to use a distributed dispersed 3 redundancy 1 volume?. You will get your 
total capacity divided by 3 times 2 (that's 2/3 of total capacity) and this 
config still tolerates one node failure at the same time.

Hope this helps.

*Ramon Selga*

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DataLab SL <http://www.datalab.es/>

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El 06/09/19 a les 17:11, Cristian Del Carlo ha escrit:
> Hi,
> I have an environment consisting of 4 nodes ( with large disks).
> I have to create a volume to contain image of virtual machines.
> In documentation i read:
> /Hosting virtual machine images requires the consistency of three-way 
> replication,
> which is provided by three-way replicated volumes, three-way distributed 
> replicated volumes,
> arbitrated replicated volumes, and distributed arbitrated replicated volumes. /
> So I'm going to confusion to configure this volume.
> I have 4 nodes and I don't want to lose space by dedicating one to the 
> function of arbiter.
> Would it be reasonable to configure the volume as in these two examples?
> # gluster volume create test1 replica 3 \
> server1:/bricks/brick1 server2:/bricks/brick1 server3:/bricks/brick1 \
> server2:/bricks/brick2 server3:/bricks/brick2 server4:/bricks/brick2 \
> server3:/bricks/brick3 server4:/bricks/brick3 server1:/bricks/brick3 \
> server4:/bricks/brick4 server1:/bricks/brick4 server2:/bricks/brick4
> # gluster volume create test1 replica 3 arbiter 1 \
> server1:/bricks/brick1 server2:/bricks/brick1 server3:/bricks/arbiter_brick1 \
> server2:/bricks/brick2 server3:/bricks/brick2 server4:/bricks/arbiter_brick2 \
> server3:/bricks/brick3 server4:/bricks/brick3 server1:/bricks/arbiter_brick3 \
> server4:/bricks/brick4 server1:/bricks/brick4 server2:/bricks/arbiter_brick4
> Thanks,
> -- 
> */
> /*
> */Cristian Del Carlo/*
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> Gluster-users at gluster.org
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