Cluster and RAID 5 Array bottleneck.( I believe)

Felix Rauch rauch at
Mon Mar 19 15:10:02 PST 2001

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

Did you try TCP measurements to see what the network can deliver? TCP
performance should be higher than NFS performance.

- Felix

Felix Rauch                      | Email: rauch at
Institute for Computer Systems   | Homepage:
ETH Zentrum / RZ H18             | Phone: ++41 1 632 7489
CH - 8092 Zuerich / Switzerland  | Fax:   ++41 1 632 1307

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