FreeBSD on Dell r210 (SAS 6/ir)

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Hi list.

We are looking for a small, cheap, decent performing 19" server to run 
FreeBSD or possibly FreeNAS, and found the Dell R210 which suits our 
needs perfectly.
However, a lot of people seem to have problems with the SAS 6/ir 
controller under FreeBSD. According to what I've found on Google, it 
works, but the performance is horrible. This is a complete showstopper 
in this case, since the plan was to use the servers as offsite storagenodes.

Does anyone have firsthand experience with the SAS 6/ir, or the PERC 
S100 in the somewhat more expensive Xeon version of the R210?
Or does anyone know of another server with similar size, that is 19" 
wide and only ~40 cm deep?