Re: [patch 2/3 v3] raid1: read balance chooses idlest disk for SSD

[Roberto Spadim <roberto@xxxxxxxxxxxxx>]

sorry about many posts, i will stop a bit now...

could we turn off disk NCQ? ok nobody want to read this, but could we
turn off NCQ and get better performace? since we do a good elevator at
linux code... maybe turn off disk cache too... (it´s only 32MB for
sata/sas, and can be alot to raid controller...), just some ideas to
get better performace... (i didn´t think before write if cache help or
not when we send I/O to disk, but check if it´s a good question or
not)

2012/7/2 Roberto Spadim <roberto@xxxxxxxxxxxxx>:
> for SSD without inteligent parts (cache and queue) i think this could
> works nice... (at least in theory)
> for USB sticks and microsd cards may work too...
>
>
> 2012/7/2 Shaohua Li <shli@xxxxxxxxxx>:
>> On Sun, Jul 01, 2012 at 11:13:42PM -0300, Roberto Spadim wrote:
>>> nice =) very very nice =)
>>> maybe to get better than this... select the disk with min(pending time)
>>>
>>> time could be estimated with something like:
>>> (distance * time/distance unit) + (blocks to read/write * time to
>>> read/write 1 block) + (non sequencial penalty time)
>>
>> I didn't think there is way to measure request time. Disks support NCQ, they
>> can dispatch several requests at one time and finish them almost at the same
>> time. I used to measure this time (to make CFQ ioscheduler self tune), but
>> failed.
>>
>> Thanks,
>> Shaohua
>> --
>> To unsubscribe from this list: send the line "unsubscribe linux-raid" in
>> the body of a message to majordomo@xxxxxxxxxxxxxxx
>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>
>
>
> --
> Roberto Spadim
> Spadim Technology / SPAEmpresarial



-- 
Roberto Spadim
Spadim Technology / SPAEmpresarial
--
To unsubscribe from this list: send the line "unsubscribe linux-raid" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html