We have Linux/Oracle servers running both RAID 5 and RAID
0+1. We haven't seen any disk problems with any of 'em. Heck,
we have one backup server running software RAID 5 on a
366-Mhz Celeron with Maxtor IDE disks that transfers several GB
of data every night--its uptime as of today is 436 days.
My feeling is that with the type of sites any of us are running that
the RAID level issue isn't that big of a deal. With modern 10k+
RPM SCSI-3 disks and caching hardware RAID controllers it'd be
tough to max 'em out. You're far more likely to saturate the PCI
bus than the disks and at that point you'd have to be moving alot
of data around.
Now, if your building a data warehouse with a database in the
100+ GB range it's a different story. But with a database like the
AIESEC has at 6-GB, RAID 5 has been fine for us.
Here's a link some of you might be interested in:
http://staff.sdsc.edu/its/terafile/
It's about building a terrabyte-size IDE array with performance
tips and benchmarks on various RAID levels.