[Ocfs2-users] read/write performance across cluster

[Sunil Mushran]

On 05/04/2011 09:56 AM, Florin Andrei wrote:
> On 05/04/2011 09:44 AM, Srinivas Eeda wrote:
>> Yes, there is locking involved. Extending a file needs an exclusive
>> lock. Grepping a file needs read lock. If the same node(lets call it
>> writer node) does extending and grepping, then grep already has a
>> compatible lock and the data is also cached on this node. When another
>> node does the grep(lets call it reader node), then it needs to acquire
>> read lock. This requires the writer node to down grade the lock which
>> requires the node to flush data to the disk. Then the reader node has to
>> read the data to the cache. So when grep is done on the reader node,
>> there are additional messages and additional I/O's to the disk are done.
> Any workarounds?
>
> Obviously doing read and append on the same node is one way.
>
> Could the logger extend the file in a different way? The software is
> homegrown, we could modify it to make it more OCFS2-friendly, if that's
> possible.

Don't append as often. IOW, make large appends and not few bytes
at a time like all loggers.

> OCFS2 settings to tinker with?

Cache coherency is not a configurable option.