ctl_cyrusdb -r performance over NFS

[Igor Brezac]

On Thu, 27 Mar 2003, Andrew McNamara wrote:

> >A SAN is just a different transport mechanism between the host and the
> >drives -- the protocol is the same old SCSI that has been around for
> >years.  That said, there is less interoperability than one would like at
> >this point.
> >
> >The basic problem with NFS is that either you violate standard Unix
> >filesystem semantics or you have pitiful performance (by disabling
> >client-side caching).  Add to that the idea that locking was an
> >after-thought (the design goal of a stateless filesystem doesn't exactly
> >fit with maintaining locks) and it is really a mess.
> >
> >As long as you only have one machine writing to the data, you don't have
> >to worry so much about broken filesystem semantics (which is why your
> >Oracle instance works), but you still have lousy performance.
>
> You assume I don't already know this... 8-)
>
> BTW, I don't think it's "violate unix semantics OR pitiful perfomance" -
> the protocol is flawed in ways that make that "violate unix semantics
> AND pitiful perfomance". In particular, lost, out of order or replayed
> requests are not fully addressed by the stateless design.
>
> For what it's worth, we go to extraordinary lengths to ensure only one
> host hits a given NFS volume at a time, we spend silly amounts of money to
> keep the latency down and the bandwidth up, and we use the best quality
> NFS implementations we can.
>

Even the best NFS implemantation cannot come close to direct attached
storage performance and stability.  If you go to great lenghts to ensure
that only one machine can access a given NFS volume, why not go to direct
attached storage?

> I'm not convined that SAN (where "storage" is a euphemism for "disk") is
> really the answer to anything. Network attached storage (where "storage"
> is a euphemism for "file server") is a far more convenient model. We just
> need a better protocol. If only Plan9 had gained a critical mass... 8-)
>

I am not sure SAN is the right term here, but fibre channel hba/fibre
channel switch (if needed)/storage array is extremely stable and fast
performing solution.  This allows you have a centraly managed storage for
just about all your platforms.  With right hardware you can also setup
network attached storage from this platform.

Maybe iSCSI is something to look at...

-- 
Igor