quad-core 2900 vs. dual-core 6850

[Jacob Bunk Nielsen]

Hi

We're in the process of replacing an old PowerEdge 6600.

But I've come in doubt if we should buy a 4 CPU dual-core 6850 with
3.4 GHz Xeon CPUs or a 2900 with two quad-core 2.66 GHz Xeon CPUs. The
2900 is a newer generation and comes with PERC5 (the 6850 comes with
PERC4, I think) and faster memory than the 6850. If I want SAS drives
in the 6850 I also have to buy a MD1000 disk box or similar.

I'm considering the 2900 and not the 2950 because the 2900 can hold
the amount of drives I need internally.

The server will be running Linux and will be used for blast and
similiar text alignment algoritms on fairly large indexed text files,
so I'll use some 15k RPM drives for storage.

Of course we have also considered the 6950. We have a HP DL585 with
dual-core Opterons, and it was superior to anything we could buy from
Dell a year ago, but since then the newer Xeon-CPUs seems to be
superior to the Opterons.

As I see it we get 8 cores with both the 6850 and the 2900. But the
2900 runs at lower clock speed but with faster memory I/O and a better
RAID-controller. Correct?

Does anyone have any input on whether we should go for the 2900 or the
6850? Price is of course a bit of an issue, but both servers are
within budget, so I'm mainly interested in hearing about performance
of the two systems.

-- 
Jacob