[sheepdog-users] Sheepdog 0.80: Queries and feedback

[Arnold Krille]

Hi,

I can only try to answer one of your questions as I am a step behind
you (haven't yet installed sheepdog but following the development since
a year).

On Wed, 12 Mar 2014 20:05:32 +0000 Struan Bartlett
<struan.bartlett at NewsNow.co.uk> wrote:
> 1. The README says you need a minimum of 3 nodes, which must be
> x86_64. Sheepdog compiles for i386, and it appears possible to format
> a cluster with 'dog cluster format -c 2' and I seem to have been able
> to run a cluster with two copies, on i386, quite stably. Is this line
> in the README just out of date? If so this is misleading and it would
> be helpful to correct it.

I think three nodes are needed because of quorum calculations. With two
nodes both online but with lost communication, both nodes think of
themself as the sole survivor and allow writing to all volumes.
With three nodes, each node knows that when it doesn't see at least one
partner, it should stop all write-access to not disturb things.

The -c option for cluster format is only to define the default
concurrency for new images afaik. You can happily format your
three-node cluster with -c 1. Or format with -c 3 and create images
without concurrency...

Have fun,

Arnold
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