[ovirt-users] Hyperconverged Setup and Gluster healing

[FERNANDO FREDIANI]

RAID 6 doesn't make exactly 3 copies of data.

I think storage is too expensive when compared to the total cost of the 
platform that 3 copies is waste of storage or luxury, given than if you 
have a permanent failure you still can make a new 2nd copy of the data 
provided you have storage left for that.


On 25/04/2017 10:26, Donny Davis wrote:
> I personally want three copies of my data, more akin to RAID 6(ish) so 
> in my case replica 3 makes perfect sense.
>
> On Mon, Apr 24, 2017 at 11:34 AM, Denis Chaplygin <dchaplyg at redhat.com 
> <mailto:dchaplyg at redhat.com>> wrote:
>
>     Hello!
>
>     On Mon, Apr 24, 2017 at 5:08 PM, FERNANDO FREDIANI
>     <fernando.frediani at upx.com <mailto:fernando.frediani at upx.com>> wrote:
>
>         Hi Denis, understood.
>         What if in the case of adding a fourth host to the running
>         cluster, will the copy of data be kept only twice in any of
>         the 4 servers ?
>
>
>     replica volumes can be build only from 2 or 3 bricks. There is no
>     way to make a replica volume from a 4 bricks.
>
>     But you may combine distributed volumes and replica volumes [1]:
>
>     |gluster volume create test-volume replica 2 transport tcp
>     server1:/b1 server2:/b2 server3:/b3 server4:/b4|
>
>     test-volume would be like a RAID10 - you will have two replica
>     volumes b1+b2 and b3+b4 combined into a single distributed volume.
>     In that case you will
>     have only two copies of your data. Part of your data will be
>     stored twice on b1 and b2 and another one part will be stored
>     twice at b3 and b4
>     You will be able to extend that distributed volume by adding new
>     replicas.
>
>
>     [1]
>     https://gluster.readthedocs.io/en/latest/Administrator%20Guide/Setting%20Up%20Volumes/#creating-distributed-replicated-volumes
>     <https://gluster.readthedocs.io/en/latest/Administrator%20Guide/Setting%20Up%20Volumes/#creating-distributed-replicated-volumes>
>
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