[Lustre-discuss] Lustre drawback

[Brian J. Murrell]

On Thu, 2007-12-13 at 17:58 +0100, Marco wrote:
> 
> "[...] Currently, one additional drawback to Lustre is that a Lustre
> client cannot be on a server that is providing OSTs.

Well it can, it is just not (yet?) a supported configuration.

Consider a machine with a Lustre client on it which is experiencing
memory pressure.  One way to deal with that is to start flushing memory
pages to disk where for a Lustre client disk can mean to an OST.

However if the OST it's trying to flush to is on the same node, that OST
will cause additional memory pressure in trying to allocate memory to
receive the pages from the client.  If the OST can't allocate memory
then the client can't flush pages to free up some of it's usage and you
now have a deadlock.

b.