I've only run Debian Squeeze on my MV2120, but my impression is that the disk performance is slower than expected. When performing large block copies from one disk to the other I see speeds of about 8 to 15 megabytes/second. It seems to me that with the disks I'm using something on the order of 35 to 50 megabytes/second or faster should be possible.
Is this the result of the ARM processor being slow, or are there perhaps other issues with the Debian install? I've noticed in past messages that people have seen much faster disk performance with the original HP firmware versus Debian.