Re: Problem identified: WAPL/RAIDframe performance problems

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

On Nov 28, 2012, at 10:19 PM, Edgar Fuß <ef%math.uni-bonn.de@localhost> wrote:

>> Writing filesystem blocks won't help.
>> RAIDframe needs writes as large as a stripe.
> Nothing prevents one from making both quantities the same value
> 
>> 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.
> As far as I understood hannken@, I'm bitten by writing to the log, not by
> flushing it.


Flushing is just writing to the log.  These writes have sizes between
512 bytes and the file system block size.  Problem is these writes
are not multiples of and are not aligned to file system block size.

Collecting the data and writing MAXPHYS bytes aligned to MAXPHYS
should improve wapbl on raid.

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