I see no point in running raid5 on a home server, but I hear that a lot of people believe this gives them some sort of added security against data-loss.
raid5 does not eliminate the need for a real oldschool backup(but hey its not my data).
You don't use RAID to eliminate backups.
You use RAID for many other reasons: Increase reliability; Increase performance; Combine physical storage to larger logical units.
In my case, I have over nearly 1TB of music cataloged in MC. I have another 500GB waiting to be cataloged. I have another 1TB of DVDs.
For my 3.5 TB in total storage space I currently have, I could simply assign a single Win* drive letter for each of the 12 drives (or otherwise create 12 shares accessed over the network solely by URIs). This would be completely absurd.
I could simply create concatenations to create a larger logical volume, but any single failure would result in a complete loss of the entire volume. If you use IDE drives and don't expect failures you are in for an awakening (FYI: Network Appliance has storage solutions based on IDE drives and documents a failure rate more than 10X of SCSI drives). Western Digital, IBM/HGS, and Maxtor have all had products that have experienced over 25% failure rates.
Using raid5 protects against single drive failures which WILL happen. If you think re-ripping 1TB of music upon failure is acceptable then by all means forgo raid. If you have an alternate "backup" solution that is more cost and time effective then by all means forgo raid. My CDs are my backups but it is in my best interest to do what I can to minimize their need - the goal is to actually
enjoy my library and not spend the rest of my life maintaining it. . .
If you only have one or two drives then you are much less likely to experience a problem, but if you have a half dozen then you're six times as likely to experience a failure. If you have a dozen you've got more than an order of magnitude greater chance for failure.