With large capacity drives (greater than 1TB), RAID5 is not a good option. The chance of a second drive failure during rebuild is very real.
For that reason, for most enterprise gear these days, for reliability with large drives, RAID10 for speed, or RAID6 (or a variant thereof) for capacity is recommended. There are also some newer block protection options that protect blocks rather than whole disks.
Sure, but all my data is backed up on a large nas raid 6 array, with a second copy on a raid5 nas... :-)
So I feel that raid5 is good enough for my live storage unit.