Besides the RAID controller, do I need two SCSI cards?
No. For hardware SCSI RAID 1 all you need is a raid controller, cable
with terminator and 2 scsi drives (should be matching size, preferably
identical drives). If you want to be fancy you can use 80pin sca
drives in a hot-swap backplane/cage. There are a lot of bad
backplanes and enclosures on the market tho. IMHO Supermicro products
are a decent value FWIW.
For only 1 RAD1 volume your choice of controller is pretty broad as
this doesn't require lots of cache or a fast processor and an older
U160 card will do just fine. In addition to the manufacturers already
mentioned that opens things up to Mylex (now owned by LSI) and in
addition some older IBM Serveraid controllers (which can often be used
on non-IBM servers). The IBM's are nice because they share a common
BIOS so an old controller is still supported through continual BIOS
and software updates. Compatibility with non-IBM machines is very
spotty though. The LSI Mylex are nice because the on-board software
is quite robust. Mylex are EOL though. Many people complain about
Adaptec performance but that should not really affect a simple volume
like this. Watch out for ZCR (zero channel raid) cards as they are
likely not what you need. They interface with a compatible on-board
scsi controller to upgrade it to raid functionality.
Make sure you review the manuals of whatever products you are
considering purchasing. With even simple RAID setups the devil is in
the details.