[Sheepdog] Databases, write barriers etc

[MORITA Kazutaka]

At Mon, 8 Aug 2011 18:29:16 +0100,
Brian Candler wrote:
> 
> On Tue, Aug 09, 2011 at 01:18:57AM +0900, MORITA Kazutaka wrote:
> > I think the performance could be a problem.  The latency of a Sheepdog
> > is higher than other local disk formats because of data replication
> > and network latency, so Sheepdog would show a poorer performance with
> > something like databases.
> 
> If an app wants to update a single block, will this require Sheepdog to
> fetch an entire 4MB object, modify part of it, and write it back?

The app sends only the data to be written, and the server daemon
overwrites the existing object.  The app doesn't fetch the entire
object.

Thanks,

Kazutaka

> 
> You're right, I need to do some performance testing.
> 
> Thanks,
> 
> Brian.
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