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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670 25 37 05
DataLab SL <http://www.datalab.es/>
Aviso Legal <http://www.datalab.es/cont_cas/legal.html>
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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