Re: stripe_cache_size and performance

[Justin Piszcz <jpiszcz@lucidpixels.com>]

I have found a 16MB stripe_cache_size results in optimal performance after 
testing many many values :)

On Fri, 22 Jun 2007, Raz wrote:

> On 6/22/07, Jon Nelson <jnelson-linux-raid@jamponi.net> wrote:
>> On Thu, 21 Jun 2007, Raz wrote:
>> 
>> > What is your raid configuration ?
>> > Please note that the stripe_cache_size is acting as a bottle neck in some
>> > cases.
>> 
>> Well, it's 3x SATA drives in raid5. 320G drives each, and I'm using a
>> 314G partition from each disk (the rest of the space is quiescent).
> what is the chunk size ?. Please note that a raid performance is dependent
> on the access pattern to the disks. What is this raid aimed to do ?
> more reads ? more writes ? If you can control the access pattern ,
> you might be able to increase performance.
>> > On 6/21/07, Jon Nelson <jnelson-linux-raid@jamponi.net> wrote:
>> > >
>> > > I've been futzing with stripe_cache_size on a 3x component raid5,
>> > > using 2.6.18.8-0.3-default on x86_64 (openSUSE 10.2).
>> > >
>> > > With the value set at 4096 I get pretty great write numbers.
>> > > 2048 and on down the write numbers slowly drop.
>> > >
>> > > However, at values above 512 the 'check' performance is terrible. By
>> > > 'check' performance I mean the value displayed by /proc/mdstat after
>> > > I issue:
>> > >
>> > > echo check > /sys/block/md0/md/sync_action
>> > >
>> > > When I say "terrible" I mean < 3MB/s.
>> > > When I use 384, the performance goes to ~70MB/s
>> > > 512.. 72-73MB/s
>> > > 640.. 73-74MB/s
>> > >
>> > > 768.. 3300 K/s. Wow!
>> > >
>> > > Can somebody 'splain to me what is going on?
>> > >
>> > > --
>> > > Jon Nelson <jnelson-linux-raid@jamponi.net>
>> > > -
>> > > To unsubscribe from this list: send the line "unsubscribe linux-raid" 
>> in
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>> > >
>> >
>> >
>> > --
>> > Raz
>> >
>> >
>> >
>> 
>> --
>> Jon Nelson <jnelson-linux-raid@jamponi.net>
>> -
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>
>
> -- 
> Raz
> -
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