Re: Raidframe and disk strategy

[buhrow%lothlorien.nfbcal.org@localhost (Brian Buhrow)]

        hello.  What I saw before the patches I submitted for NetBSD-5, 6 and
current was that processes would get stuck in biowait and the disks were
incredibly busy without as much throughput.  By setting the raidframe
strategy to be the same as the underlying disk strategy, I got about a 15%
improvement in throughput.  NetBSD-6 and -current allow you to set the disk
strategies of wd and sd disks, NetBSD-5 only allows changing of the
strategy of wd disks.  The complete patch for -current sets the strategy of
raidframe to the default strategy for the system, rather than fcfs.
That change made it into NetBSD-6 as well, but not into NetBSD-5.
For NetBSD-5, you need to manually set the disk strategy with dkctl(8) in
/etc/rc.local or something like that.  Since dkctl can be run on the fly,
you can easily test various disk sorting strategies, comparing the
throughput of having the raidframe strategy match the disks, versus having
it use fcfs regardless of what the disks are doing, as well as testing
various disk strategies on all levels of your storage subsystem.  I have
found that for my work loads, using the priocscan sorting algorithm on both
the disks and the raid sets yields the best performance.


-Brian

On Oct 16,  5:54pm, Edgar =?iso-8859-1?B?RnXf?= wrote:
} Subject: Re: Raidframe and disk strategy
} > More thoughts?
} Sorry, no, but two questions:
} 
} I may also be suffering from the same sorting problem.
} In case I am, which channel would the affected processes be waiting on?
} 
} Instead of adapting RAIDframe's sorting to the disc drivers', would it make 
} sense to adapt the other way round? There is nothing but RAIDs on my discs.
>-- End of excerpt from Edgar =?iso-8859-1?B?RnXf?=