FIO r/w to 2 disks

FIO r/w to 2 disks

[Strickland, Carl]

Hi All,

I'm performing a series of time-based storage tests and need FIO to read and
write to separate disks, in the ratio specified (e.g. 80/20).

I've performed initial tests with two FIO instances (one read, one write), but
found that in one scenario I get a ratio of ~50/50 and in another I get
~60/40. However, in order to compare the results of these tests, their ratios
must be approximately equal.

Is it possible to achieve this with a single FIO instance? Do you have any
recommendations for achieving a specific ratio with two FIO instances?

All help is greatly appreciated!


Thanks,
Carl

Re: FIO r/w to 2 disks

[Jens Axboe]

On 2012-06-08 21:52, Strickland, Carl wrote:
> Hi All,
> 
> I'm performing a series of time-based storage tests and need FIO to read and
> write to separate disks, in the ratio specified (e.g. 80/20).
> 
> I've performed initial tests with two FIO instances (one read, one write), but
> found that in one scenario I get a ratio of ~50/50 and in another I get
> ~60/40. However, in order to compare the results of these tests, their ratios
> must be approximately equal.
> 
> Is it possible to achieve this with a single FIO instance? Do you have any
> recommendations for achieving a specific ratio with two FIO instances?

It's not clear from your email exactly what kind of job(s) you ran. Have
you tried a single job with rwmix set? rwmixread=80 and rw=randrw should
give you the requested ratio, 80% reads and 20% writes.

-- 
Jens Axboe

RE: FIO r/w to 2 disks

[Strickland, Carl]

Hi Jens,

The test I'm interested in performing would require (I believe) FIO to read
from one device and write to another in a specified ratio. This is different
from the rwmix feature in FIO, as I can specify only a single device where the
reads and writes will take place.

Assuming that I could achieve the same read/write ratio with two FIO instances
(one reading from one device and the other writing to a different device) as I
get using a single FIO instance and rwmix, is there a reason--in terms of how
reads and writes would be performed--that would prevent a valid comparison
between the two?


Thanks,
Carl

Re: FIO r/w to 2 disks

[Jens Axboe]

On 06/15/2012 01:41 AM, Strickland, Carl wrote:
> Hi Jens,
> 
> The test I'm interested in performing would require (I believe) FIO to
> read from one device and write to another in a specified ratio. This
> is different from the rwmix feature in FIO, as I can specify only a
> single device where the reads and writes will take place.
> 
> Assuming that I could achieve the same read/write ratio with two FIO
> instances (one reading from one device and the other writing to a
> different device) as I get using a single FIO instance and rwmix, is
> there a reason--in terms of how reads and writes would be
> performed--that would prevent a valid comparison between the two?

Maybe the flow options would help you? Set up two jobs in a single file,
one reader and one writer. Set up the flow parameters to get your
desired split. See HOWTO, and/or examples/flow to get an idea for how to
use that.

-- 
Jens Axboe

RE: FIO r/w to 2 disks

[Strickland, Carl]

Thanks Jens, I will look into it!


Cheers,
Carl Strickland

-----Original Message-----
From: fio-owner@vger.kernel.org [mailto:fio-owner@vger.kernel.org] On Behalf Of Jens Axboe
Sent: Thursday, June 14, 2012 11:50 PM
To: Strickland, Carl
Cc: fio@vger.kernel.org
Subject: Re: FIO r/w to 2 disks

On 06/15/2012 01:41 AM, Strickland, Carl wrote:
> Hi Jens,
> 
> The test I'm interested in performing would require (I believe) FIO to 
> read from one device and write to another in a specified ratio. This 
> is different from the rwmix feature in FIO, as I can specify only a 
> single device where the reads and writes will take place.
> 
> Assuming that I could achieve the same read/write ratio with two FIO 
> instances (one reading from one device and the other writing to a 
> different device) as I get using a single FIO instance and rwmix, is 
> there a reason--in terms of how reads and writes would be 
> performed--that would prevent a valid comparison between the two?

Maybe the flow options would help you? Set up two jobs in a single file, one reader and one writer. Set up the flow parameters to get your desired split. See HOWTO, and/or examples/flow to get an idea for how to use that.

--
Jens Axboe

--
To unsubscribe from this list: send the line "unsubscribe fio" in the body of a message to majordomo@vger.kernel.org More majordomo info at  http://vger.kernel.org/majordomo-info.html