Re: Problem identified: WAPL/RAIDframe performance problems

["J. Hannken-Illjes" <hannken%eis.cs.tu-bs.de@localhost>]

On Nov 28, 2012, at 10:13 PM, Michael van Elst <mlelstv%serpens.de@localhost> 
wrote:

> gdt%ir.bbn.com@localhost (Greg Troxel) writes:
> 
>> I wonder if it's possible (easily) to make the log only use fsbize
>> boundaries, (maybe forcing it to be bigger as a side effect.)
> 
> Writing filesystem blocks won't help. RAIDframe needs writes as large
> as a stripe.

The file system block size should match the raid stripe size or you
have much more problems than flushing the log.

> The log itself could write much larger chunks but flushing is done
> in a series of writes as small as a single physical block. I think
> the only way to improve that is to copy everything first into a
> large buffer. Not very efficient.

Needing to copy say 8 Mbytes of data and writing it in big chunks
will be much faster than writing it many smaller unaligned segments.

--
J. Hannken-Illjes - hannken%eis.cs.tu-bs.de@localhost - TU Braunschweig 
(Germany)