DR4000: Slow read performance using NFS

Hi,

We're setting up our first DR4000 de-duplicator to assist the backup system. While doing some basic performance tests, I discovered that the read performance using the NFS protocol is really, really bad. Using a 1 Gbit/s connection, I set up a Linux client using both NFS and CIFS to access the DR4000. No routers or firewalls are involved, the two nodes are on the same network segment with only 2 switch hops in between. We currently don't use bonding, just one of the DR4000's two network interfaces is connected. The network segment and the DR4000 was practically idle at the time of testing.

I wrote and read large (multi-gigabyte) files and measured the performance:

Write over CIFS: ~90 MB/s (really good)

Read over CIFS: ~110 MB/s (practically wire-speed)

Write over NFS: ~112 MB/s (superb!)

Read over NFS: ~25 - 40 MB/s, typically  ~32 MB/s. <= This is not even close to being acceptable!

So my question is, what can be done to improve the read performance over NFS? Clearly, the DR4000 can deliver better than this.

/Jan