[sheepdog-users] Doc. url

[Andrew J. Hobbs]

On 11/01/2013 09:50 AM, Daniel Dehennin wrote:

Valerio Pachera <sirio81 at gmail.com><mailto:sirio81 at gmail.com> writes:



2013/10/28 Daniel Dehennin <daniel.dehennin at baby-gnu.org><mailto:daniel.dehennin at baby-gnu.org>:



When I'm in single node mode, I would like to have some local data
replication between disks à-la RAID5.



I think this is out of the scope of sheepdog.
Also because the host devices may be very different from each other.
E.g. I have a host with 2 disks: 500G and 2T.
You can't apply raid logic in such case without wasting lot's of space.



I saw on the wiki[1] that multi-disks on a single host work à-la RAID0.

I'm not sure about the informations on that page, it's said that:

    “To conclude, MD will make best performance out of underlying disks
    like RAID-0 and have recovery capability without using extra parity
    storage (RAID5) or replicating storage (RAID10).”

But I'm not sure if the recovery will use copy from other nodes in the
sheepdog cluster or if it works locally.

Thanks.

Footnotes:
[1]  https://github.com/sheepdog/sheepdog/wiki/Multi-disk-on-Single-Node-Support




It seems like you'd be able to achieve something like this in the mode of running multiple sheepdog services, each with a unique port, and each writing to a separate disk.  Similar to how you might use it while developing it.  I suppose if you had 6+ disks you could run erasure vdis which would give (using 4:2) something very similar to Raid 6, although not quite the same.  For a single host, you'd be better off running md or hardware RAID directly.

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