[CentOS] Optimum Block Size to use

[Leon Fauster]

Am 19.08.2015 um 10:24 schrieb John Hodrien <J.H.Hodrien at leeds.ac.uk>:
> On Wed, 19 Aug 2015, Jatin Davey wrote:
> 
>> Hi All
>> 
>> We use CentOS 6.6 for our application. I have profiled the application and find that we have a heavy requirement in terms of Disk writes. On an average when our application operates at a certain load i can observe that the disk writes / second is around 2 Mbps (Average).
> 
> Initial thought is, do you really care?  2Mbps is peanuts, so personally I'd
> leave everything at the defaults.  There's really no need to optimise
> everything.
> 
> Obviously the exact type of writes is important (lots of small writes written
> and flushed vs fewer big unsynced writes), so you'd want to poke it with
> iostat to see what kind of writes you're talking about.



to address this we use (sysctl)

vm.dirty_expire_centisecs 
vm.dirty_writeback_centisecs

furthermore check the fs alignment with 
the underlying disk ...

--
LF