[Gluster-devel] Striping.

[Chris Johnson]

On Fri, 30 Nov 2007, Anand Avati wrote:

      So my single brick test with readahead was also too simple.  I
tried that and also saw no improvement.

      Does it matter which order readahead and writebehind are done in?

> Yes, also you should be using read-ahead on the client side to leverage read
> throughput with stripe (else it would end up serial alternative reads). Also
> write-behind should be used for acheiving the aggregated disk throughput
> with stripe.
>
> avati
>
> 2007/11/29, Chris Johnson <johnson at nmr.mgh.harvard.edu>:
>>
>> On Thu, 29 Nov 2007, Anand Avati wrote:
>>
>>       So what I'm hearing is that my test iss too simple.  That right?
>>
>>> Chris,
>>> you will see the help of stripe when you perform IO where disk head is
>> the
>>> bottleneck. For example try to dd a file > 2x RAM size. Then dd with
>> stripe.
>>> you will note that the 'rock bottom throughput' is lifted higher with
>>> stripe. It also helps when one file is accessed by a LOT of clients so
>> that
>>> one machine's IO does not become a bottleneck.
>>>
>>> avati
>>>
>>> 2007/11/29, Chris Johnson <johnson at nmr.mgh.harvard.edu>:
>>>>
>>>>       Hi again,
>>>>
>>>>       So I did my dd read test of my 24MB file on a simple two brick
>>>> stripe.  Nothing fancy.  Two bricks and the stripe define on the server
>>>> side.  Client side mounts the remote stripe.  Default block size,
>>>> 128KB.
>>>>
>>>>       No difference between that and my single brick test as far as
>>>> time goes.  What's striping supposed to get me?  I thought it was
>>>> drives heads.  Or am I missing something again?
>>>>
>>>>
>> -------------------------------------------------------------------------------
>>>>
>>>> Chris Johnson               |Internet: johnson at nmr.mgh.harvard.edu
>>>> Systems Administrator       |Web:
>> http://www.nmr.mgh.harvard.edu/~johnson
>>>> <http://www.nmr.mgh.harvard.edu/%7Ejohnson>
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>>>>
>>>>
>> -------------------------------------------------------------------------------
>>>>
>>>>
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>>>>
>>>
>>>
>>>
>>> --
>>> It always takes longer than you expect, even when you take into account
>>> Hofstadter's Law.
>>>
>>> -- Hofstadter's Law
>>>
>>
>>
>> -------------------------------------------------------------------------------
>> Chris Johnson               |Internet: johnson at nmr.mgh.harvard.edu
>> Systems Administrator       |Web:
>> http://www.nmr.mgh.harvard.edu/~johnson
>> NMR Center                  |Voice:    617.726.0949
>> Mass. General Hospital      |FAX:      617.726.7422
>> 149 (2301) 13th Street      |What the country needs is dirtier fingernails
>> and
>> Charlestown, MA., 02129 USA |cleaner minds.  Will Rogers
>>
>> -------------------------------------------------------------------------------
>>
>
>
>
> -- 
> It always takes longer than you expect, even when you take into account
> Hofstadter's Law.
>
> -- Hofstadter's Law
>

------------------------------------------------------------------------------- 
Chris Johnson               |Internet: johnson at nmr.mgh.harvard.edu
Systems Administrator       |Web:      http://www.nmr.mgh.harvard.edu/~johnson
NMR Center                  |Voice:    617.726.0949
Mass. General Hospital      |FAX:      617.726.7422
149 (2301) 13th Street      |A lifetime is more than sufficiently long
Charlestown, MA., 02129 USA |to get what there is of it wong.   Piet Hein
-------------------------------------------------------------------------------