[Ocfs2-users] read/write performance across cluster

[Florin Andrei]

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.

OCFS2 settings to tinker with?

> Just curious, do you have any numbers to show the time difference?

Not as of now. I switched it back to "fast mode" (read and append on the 
same node) because it was pretty annoying. I'll see if I can run some 
tests one of these days.

-- 
Florin Andrei
http://florin.myip.org/