Do you rely on RAID as your NAS backup?

I agree with the comments above.  See the posts by me and by Kijanki in this thread regarding the shortcomings of RAID as a backup solution.  Also, regarding cloud backup, as I said in that thread...

... I would have to say it is not a desirable solution, at least as the primary backup solution for a large music collection. While incrementally uploading the files for backup purposes, over time, should be fine in most cases, consider what would happen if the entire library had to be downloaded due to failure of the local hard drive(s). Even making the optimistic assumptions that the user's interconnect connection is as fast as 100 mbps, and that the download speed is not limited by the responsiveness of the server at the other end or by any servers in the route through the Internet that is in between, downloading say 2 terabytes of music would require approximately 56 hours of non-stop downloading. And under less optimistic assumptions about the speed of the download process, that could conceivably stretch out to several weeks. 

Regards,
-- Al
 

Ozzy, see this Wikipedia writeup re RAID.

Regards,
-- Al
 

I use a Synology DS2125j with 2 WD 3GB Red drives as the primary drive for music and TimeMachine for my iMac. I don't keep the music file set on the iMac where I have a large file set of photographs. Had a very capable 5 year old ReadyNAS but swapped it out and enjoy the same fast performance and features but with a more intuitive interface. The configuration is their SHR - effectively RAID 1- a simple sync between the 2 drives. The Synology is wired to the router with my iMac which I use to download and rip music. Following this I use ChronoSync wirelessly to update my mac mini which hosts the music for my system. I also have 2 WD 1TB Passports, 1 for each computer,  which I configure as 'bootable' and update every 2 weeks for offsite storage (a friend's house) 'cause, as safestanil mentioned above, RAID is not failsafe. So effectively I have the original rips on the Synology with a hot copy, a copy on the mac mini and an off site copy.  It's rather a belt and suspenders arrangement but for around $500.00 will provide back-up for almost any local disaster. There are tempting cloud solutions and I may consider them but discovered that uploading large file sets can be verrrrrrrrry long - days, or months if it's the initial upload. And to perform an entire restore usually requires the provider send an expensive hard disk. 
Speed is not an issue in either importing new music or synchronizing between the 2 macs (other than the original load to the mac mini of 800 albums). Kept the hard copies and hope to never have to re-rip them again. 

As has been pointed out above, RAID is good for some things but not a complete disaster recovery solution.  I definitely agree with @almarg (not unusual) about the time to recover your backed-up data from the cloud.  RAID (not RAID 0) is good for recovery from things that don't cause you to lose the whole array.  It's not going to help you in case of fire, theft, tornadoes, etc.

A few years back I ran across an article from a company called Backblaze that offers cloud storage services.  Because they purchase large numbers of drives, know when they put them in service and (obviously) know when they fail, they are in a good position to comment on the reliability of different brands and sizes.  In the article I read, they commented on a high failure rate among 3 TB drives.  Because of that I have steered away from buying that size drive.  That's probably too general but your data is valuable even if it can be replaced so I don't take the chance.  If you're interested you can do an internet search on "backblaze hard drive reliability" and find plenty of references.  The most recent one I saw after a short search is here.

Dick

I use a western digital raid enabled NAS for all my digital music. It is in turn is backed up incrementally to the cloud via Crashplan, which offers unlimited backup, no-throttle, backups. Crashplan will also deliver via overnight delivery physical drives to you in the event that you need a full restore (i haven't needed that yet). Very happy with it and have been using it for around three years. western digital drives, in my experience, are very reliable.

no affiliation with either company.