Re: [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 <address@hidden>:
> > 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 <address@hidden>:
> > > >       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: address@hidden
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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: address@hidden
> > 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: address@hidden
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
-------------------------------------------------------------------------------