Cluster and RAID 5 Array bottleneck.( I believe)

Velocet mathboy at
Mon Mar 19 17:11:11 PST 2001

On Tue, Mar 20, 2001 at 12:10:02AM +0100, Felix Rauch's all...
> On Thu, 15 Mar 2001, Leonardo Magallon wrote:
> > When we start our job here, the switch passes no more than 31mb/s at
> > any moment.
> It could very well be the case that this number is the maximum that
> the NFS server can deliver. We had a diploma thesis here in 1999 [1]
> which examined the performance of NFS on Linux with various parameters
> such as CPU speed, network, etc.

> At that time, a 400 MHz PII as NFS server could not deliver more than
> 25 MB/s from the cache to an NFS client over Gigabit Ethernet (for
> large single files). And that was only possible with the optimal
> configuration for short times. Sustained bandwith was lower.
> I don't know the details of your server, but 35 MB/s seems likely to
> be the maximum that the NFS servers memory system and CPU can
> deliver.
> Did you try TCP measurements to see what the network can deliver? TCP
> performance should be higher than NFS performance.

NFSv3 should show a DRASTIC improvement on these stats, though I dont
have any equipment to test this (only GbE could do this as FastEther (100Mbps)
is a theoretical max of 12.5Mbps, which NFSv3 does with ease in our operations

You might also want to check out the nbd (network block device) in linux
2.4 - mounting a filesystem on an nbd is supposedly even faster than
nfs. Perhaps I can get Ben LaHaise of redhat to comment here.. (bcc'd
in case he doenst want his address known).


> - Felix
> [1][html|pdf]
> -- 
> Felix Rauch                      | Email: rauch at
> Institute for Computer Systems   | Homepage:
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Ken Chase, math at  *  Velocet Communications Inc.  *  Toronto, CANADA 

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