RE: [bgl-discuss] Blue Gene slow I/O

["Sindhi, Abdul Waris" <abdul.sindhi@xxxxxxxxxx>]

I am not sure I asked this already, but are the reads/writes buffered
on the Blue Gene ?

Waris 

-----Original Message-----
From: Sindhi, Abdul Waris 
Sent: Monday, December 04, 2006 3:51 PM
To: 'Ray Loy'; William Gropp
Cc: Sindhi, Abdul Waris; discuss@xxxxxxxxxxxxxxx
Subject: RE: [bgl-discuss] Blue Gene slow I/O 

No, the 20-30 times slower is compared to the local NFS here at Pratt. 
I re-ran my case here locally to simulate what happens on the Blue Gene.

The reads/writes are pathologically slow for us. For example in one 
of our cases where it takes 3-4 mins for us to write a ~20MB file 
here locally on the Blue Gene it looks like it would take 8 hrs or so. 

I have also ran my initial tests using the /pvfs disk. Do I need 
to link with any special libraries to use this ? Because my initial 
tests results look more slower than NFS for our application.

Waris 

-----Original Message-----
From: Ray Loy [mailto:rloy@xxxxxxxxxxx] 
Sent: Monday, December 04, 2006 1:24 PM
To: William Gropp
Cc: Sindhi, Abdul Waris; discuss@xxxxxxxxxxxxxxx
Subject: Re: [bgl-discuss] Blue Gene slow I/O 


> waris wrote:
>  The case we currently run
> is out of user homedir.


Waris has been writing to NFS so they're saturating the server.  We've
suggested using PVFS instead, which he is testing out now I believe.



> The read/write performance looks pathologically slow at around 20-30 times
> slower when compared to normal runs.


waris, is that comparison to workstations with local /tmp disks ?



ray

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