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<div class="moz-cite-prefix">Hi Carlo,<br>
<br>
Very good question: IMO it's a matter of compromise between having
lots of small files to heal and how long it takes to heal each one
shard.<br>
<br>
With small shards, it increases probability to have to self-heal
more files in a failure, also it means latency in metadata of each
file could be significant versus time to transfer rsync deltas.<br>
<br>
With big shards, time to rsync could be very long.<br>
<br>
You need to find a size something enough big for avoid latency
affects significantly to self-heal process and so small to avoid
rsync delta take too much time....<br>
<br>
We found 256MB shard size for distributed-replicated (replica 2 o
3) volumes is good enough and also we recommend to use 512MB shard
size for volumes distributed-dispersed 3 redundancy 1. For volumes
distributed-dispersed 6 redundancy 2 we use 1024MB as shard size.<br>
<br>
Hope this helps!<br>
<br>
El 07/09/19 a les 15:04, Cristian Del Carlo ha escrit:<br>
</div>
<blockquote type="cite"
cite="mid:CAF4d_RSoZtihifHNO2kNjLATs6e+1e6x-GAJ0gRdxRxaZsh6kg@mail.gmail.com">
<div dir="ltr">
<div>Thank you Ramon for your answer.</div>
<div><br>
</div>
<div>The only thing I can't understand is why to use such a big
shard?</div>
<div>The default is 64MB. I thought maybe to decrease it, I
wanted to do some tests on it.</div>
<div><br>
</div>
<div>Best regards,<br>
</div>
<div><br>
</div>
</div>
<br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">Il giorno ven 6 set 2019 alle
ore 23:09 Ramon Selga <<a
href="mailto:ramon.selga@gmail.com" moz-do-not-send="true">ramon.selga@gmail.com</a>>
ha scritto:<br>
</div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px
0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
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<div class="gmail-m_-5423031927693632057moz-cite-prefix">Hi
Cristian,<br>
<br>
Both approaches are correct but they have different usable
capacity and tolerance to node failures.<br>
<br>
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.<br>
<br>
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.<br>
<br>
For VM usage remember to enable sharding with a shard size
of 256MB at least before use volume.<br>
<br>
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.<br>
<br>
Hope this helps.<br>
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El 06/09/19 a les 17:11, Cristian Del Carlo ha escrit:<br>
</div>
<blockquote type="cite">
<div dir="ltr">Hi,<br>
<br>
I have an environment consisting of 4 nodes ( with large
disks).<br>
I have to create a volume to contain image of virtual
machines.<br>
<br>
In documentation i read:<br>
<i>Hosting virtual machine images requires the
consistency of three-way replication, <br>
which is provided by three-way replicated volumes,
three-way distributed replicated volumes, <br>
arbitrated replicated volumes, and distributed
arbitrated replicated volumes. </i><br>
<br>
So I'm going to confusion to configure this volume.<br>
I have 4 nodes and I don't want to lose space by
dedicating one to the function of arbiter.<br>
<br>
Would it be reasonable to configure the volume as in
these two examples?
<div><br>
</div>
<div># gluster volume create test1 replica 3 \<br>
server1:/bricks/brick1 server2:/bricks/brick1
server3:/bricks/brick1 \<br>
server2:/bricks/brick2 server3:/bricks/brick2
server4:/bricks/brick2 \<br>
server3:/bricks/brick3 server4:/bricks/brick3
server1:/bricks/brick3 \<br>
server4:/bricks/brick4 server1:/bricks/brick4
server2:/bricks/brick4 <br>
</div>
<div><br>
</div>
<div># gluster volume create test1 replica 3 arbiter 1 \<br>
server1:/bricks/brick1 server2:/bricks/brick1
server3:/bricks/arbiter_brick1 \<br>
server2:/bricks/brick2 server3:/bricks/brick2
server4:/bricks/arbiter_brick2 \<br>
server3:/bricks/brick3 server4:/bricks/brick3
server1:/bricks/arbiter_brick3 \<br>
server4:/bricks/brick4 server1:/bricks/brick4
server2:/bricks/arbiter_brick4 </div>
<div><br>
</div>
<div>Thanks,</div>
<div><br>
</div>
<div>-- <br>
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class="gmail-m_-5423031927693632057gmail_signature">
<div dir="ltr">
<div><span></span><span></span><br>
</div>
<div><font><b><font color="#990000"><i><br>
</i></font></b></font></div>
<div><font><b><font color="#990000"><i>Cristian
Del Carlo</i></font></b><br>
</font></div>
<br>
</div>
</div>
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