[Sheepdog] Object node affinity

[HaiTing Yao]

On Wed, May 9, 2012 at 6:40 PM, Matthew Law <matt at webcontracts.co.uk> wrote:

> Can someone please explain to me how this scenario works in sheepdog?
>
> Suppose I have 12 nodes (either 12 servers with one dedicated sheep disk
> each, or 4 servers with 3 sheep disks in each) and I want 3 copies of my
> data to be maintained.  Is it possible that none of my data will reside on
> the host which creates/accesses it or does sheepdog ensure the data has an
> affinity for the host that uses it?


There is no the affinity. The data's storage location depends on its hash
value. It perhaps resides on the host created the VM, but there is no
affinity.

You can try the object cache. The cache will keep data on local host.

If there is one local copy,  request will read the copy at first and will
not retieve the remote copies.

FYI

Thanks
Haiti



>  If it has a complete local copy does
> it still retrieve remote copies?
>
> Hope this makes sense.  I'm just interested in the efficiency of VM
> storage access in sheepdog.  If I can understand it then I will add this
> as a FAQ item for proposed user documentation.
>
> Thanks,
>
> Matt.
>
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