Re: Tuning ext3 for large disk arrays

[Badari Pulavarty <pbadari@us.ibm.com>]

On Tue, 2005-06-14 at 16:06, Peter Chubb wrote:
> Hi folks,
>    We've been doing a few scalability measurements on disk arrays.  We
> know how to tune xfs to give reasonable performance.  But I'm not sure
> how to tune ext3, and the default parameters give poor performance.
> 
> See http://scalability.gelato.org/DiskScalability/Results for the
> graphs.
> 
> iozone for 24 10k SATA disks spread across 3 3ware controllers gives a
> peak read throughput on XFS of around 1050M/sec; but ext3 conks out
> at around half that.  The maximum single threaded read performance we
> got was 450M/sec, and it's pretty constant from 12 through 24
> spindles.  We see no difference between setting -E stride=XX and
> leaving this parameter off.
> 
> The system uses 64k pages; we can set XFS up with 64k blocks; it may
> be that part of the problem is that ext3 can't use larger blocks.  We
> repeated the XFs measurements configuring the kernel and filesystem to
> use 4k pages/blocks, and although the throughput is lower than with
> the 64k page size, it's still significantly better than with ext3.
> Moreover, configuring XFS with 4k blocks, but using 64k pages gives
> results (not shown on the Wiki page) almost the same as the 64k
> pages/64k blocks.
> 

Ted mentioned that you can force ext3 mkfs to use "64k" as blocksize
through "-b 65536" option.

And also, while using 64K blocksize - can you compare performance with
other mount options like: "writeback" and  "nobh,writeback" ? 
I am curious.

Thanks,
Badari



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