On Wed, Oct 05, 2005 at 03:57:55PM -0400, Ralph Armstrong
wrote:> I am guessing it is an allocation size (i.e. how much space gets allocated
> at one time), but that is just my guess. Filesystem performance appears to
That is correct. A cluster is the minimum unit of allocation.
> improve with a larger cluster size set, suggesting that setting a larger
> cluster size causes few locks on the filesystem during a write.
It's not so much about locking, really. Allocation of one
cluster comes from a node-local allocator. It's about repetition.
Note that "performance appears to improve" is only true with
regard to simple allocation. The reduced granularity of larger cluster
sizes can have negative impacts on many workloads that involve small
files.
Basically, tune your clustersize to your workload.
Joel
--
"I'm drifting and drifting
Just like a ship out on the sea.
Cause I ain't got nobody, baby,
In this world to care for me."
Joel Becker
Principal Software Developer
Oracle
E-mail: joel.becker@oracle.com
Phone: (650) 506-8127