Advice on aacraid, Dell 1U server

[Rory Campbell-Lange <rory@campbell-lange.net>]

I'm thinking of ordering a Dell PowerEdge 1550 1U rackmount server for
the office to act as a backup server. The 1U form factor is important to
us.

For 2200 pounds one gets a Pentium III/133MHz 256K cache, 512Mb RAM,
108Gb 10,000rpm Ultra3 SCSI box with 3 years on-site service.

For another approx 140 pounds we can get hardware raid, using aacraid
v1.0.6.

3 questions:
How much of the 108Gb are we likely to lose to RAIDing? (Presumably
RAID5?)
Is aacraid reliable? We are using Mylex on the VALinux boxes.
Any recommendations for this box, apart from the price?

Thanks for any help.
Rory