[Beowulf] Software Raid

[Michael T. Prinkey]

I can tell you from long experience that this is not true.  I have had
software raid/NFS/SMB servers on our clients' LANs serving up terabytes of
home directories to tens of workstations and hundreds of compute nodes.  
Our experience is that (at least 3ware) hareware raid is significantly
slow than software raid when using the same hardware.  In fact, the
speedup in using the 8-port 3ware SATA drivers in JOBD mode with Software
RAID5 was about six times faster than using hardware RAID5 on the same
controller.

The CPU needed to do the parity computation is easily supplied by a single 
processor system.  Most of our servers our not SMP unless they are also 
asked to do something else, like act as the head node to a cluster.

There are different arguments about whether or not Linux NFS is ready to 
serve large numbers of simulateous hosts to which I am not able to speak, 
but for 10-100 users with 100s of CPUs, software RAID/NFS/SMB under Linux 
seems to work just fine.

Mike Prinkey

On Mon, 12 Dec 2005, Paul wrote:

> I read in a post somewhere that it was not possible to use a Linux 
> software RAID configuration for shared file storage in a cluster. I know 
> that it is possible to use software RAID on individual compute nodes but 
> the post stated that software RAID would not support properly support 
> simultaneous accesses on a file server. Is this true?
> 
> Assuming that hardware RAID is required (or at least preferable) I was 
> wondering if the built in RAID on some motherboards would be adequate or 
> do we need to look into a dedicated piece of hardware. We will have 
> about 10 - 12 cpus initially that will be connected with giganet 
> network. We currently have about a terrabyte of storage space and are 
> planning to mount it using NFS in a RAID 5 configuration. Our 
> applications for now will be database intensive bioinformatics apps. I 
> would be very interested in any comments. Thanks
> 
> Paul Mc Kenna
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