[CentOS] connection speeds between nodes

Tue Mar 8 17:02:38 UTC 2011
John Hodrien <J.H.Hodrien at leeds.ac.uk>

On Tue, 8 Mar 2011, Ross Walker wrote:

> The OP wanted 90MB/s per node and we have no clue whether the application he is using is capable of driving 1MB block sizes.

I thought he wanted 90MB/s reads per node (and I've demonstrated that's doable
with NFS).  The only reason I'm not showing it with four clients is because
that machine only has two GigE interfaces, so it's not going to happen with
any protocol.  That also showed ~80MB/s writes per node.

> Why wouldn't you want safe writes? Is that like saying, and if you care for
> your data?

The absolute definiton of safe here is quite important.  In the event of a
power loss, and a failure of the UPS, quite possibly also followed by a
failure of the RAID battery you'll get data loss, as some writes won't be
committed to disk despite the client thinking they are.

Now personally, I'll gladly accept that restriction in many situations where
performance is critical.

jh