[Gluster-users] how many hosts could be down in a 12x(4+2) distributed dispersed volume?

[Serkan Çoban]

If you add bricks to existing volume one host could be down in each
three host group, If you recreate the volume with one brick on each
host, then two random hosts can be tolerated.
Assume s1,s2,s3 are current servers and you add s4,s5,s6 and extend
volume. If any two servers in each group goes down you loose data. If
you chose random two host the probability you loose data will be %20
in this case.
If you recreate volume with s1,s2,s3,s4,s5,s6 with one brick on each
host any random two servers can go down. If you chose random two host
the probability you loose data will be %0 in this case.

On Mon, Sep 18, 2017 at 10:39 PM, Mauro Tridici <mauro.tridici at cmcc.it> wrote:
> Dear All,
>
> I just implemented a (6x(4+2)) DISTRIBUTED DISPERSED gluster (v.3.10) volume based on the following hardware:
>
> - 3 gluster servers (each server with 2 CPU 10 cores, 64GB RAM, 12 hard disk SAS 12Gb/s, 10GbE storage network)
>
> Now, we need to add 3 new servers with the same hardware configuration respecting the current volume topology.
> If I'm right, we will obtain a DITRIBUTED DISPERSED gluster volume with 12 subvolumes, each volume will contain (4+2) bricks, that is a [12x(4+2)] volume.
>
> My question is: in the current volume configuration, only 2 bricks per subvolume or one host could be down without losing data. What it will happen in the next configuration? How many hosts could be down without losing data?
>
> Thank you very much.
> Mauro Tridici
>
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