Re: NFS Help! Terrible performance with sync, fast performance with async

On Sun, 2006-11-19 at 04:58 -0500, Chris Wornell wrote:

> For testing, I'm using bonnie++. The following are some sample test
> results that sum up the problem:
> 
> Test on NFS server directly (not NFS loopback)
> -Sequential File Creation: 2976
> -Sequential File Deletion: N/A
> -Random File Creation: 3077
> -Random File Deletion: 9922
> 
> NFS test with sync enabled
> -Sequential File Creation: 39
> -Sequential File Deletion: 79
> -Random File Creation: 39
> -Random File Delection: 65
> 
> NFS test with async enabled
> -Sequential File Creation: 575
> -Sequential File Deletion: 1718
> -Random File Creation: 543
> -Random File Deletion: 1228
> 
I'm not sure that this comparison is fair at all.  When you ran the test
on the NFS server directly, did you use sync (I'm not that familiar with
bonnie++ so I don't know what it does by default).  Running NFS sync
would be comparable to running locally with the sync option since this
forces ALL operations to be synchronous.

Basically, for a fair comparison you need to mount the local filesystem
with the "sync" option and run the test locally and then compare those
numbers to the "sync" option with NFS.  To me it's not at all surprising
that "sync" operation would be MUCH slower for items like file creation,
even on local disks.

It's possible that bonnie++ runs in sync mode, but once again I'm not
that familiar with it.

Later,
Tom



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