I get asked this question just about every week.
As MichaelEzra and foto-z point out, a single failure on a RAID-1 array means you are one failure away from losing everything you've stored there. For those who think that double-drive failures aren't really something to worry about, I have some anecdotal experience to share:
This morning at about 6 AM GMT we had a failure in the RAID array of our forums database server. Our RAID-5 array would have been able to withstand losing one disk but apparently two died at the same time...
January 18th, 2008
Phil Askey
Editor, DPReview.com
(RAID-5, like RAID-1 can only withstand a single drive failure).
Any robust backup strategy requires a minimum of two backups--one local, and one remote.
Local Backup should protect against hard drive failure or even accidental/malicious deletion, depending on your situation. (Do you have staff to worry about malice, and are you comfortable relying on the backups themselves to recover from accidents?)
My photography is very important to me, so I recommend doubly-redundant RAID. There are only two common ways to get doubly redundant RAID: RAID-6 or RAID-50. Either of these schemes will allow any two drives to fail and still maintain integrity.
I recommend an automatic backup system which can grow with your needs--typically that's RAID, but if everything you do will fit on a disk, external backup is also OK. I am lazy. I'll always be behind if I have to go back up stuff to CD or DVD. Will the discs even work when it comes time to read them? Just keep in mind that manual backup is very time consuming.
MichaelEzra, you should know that you are
not fully doubly protected with your RAID-10 array. If two drives from the same stripe set go down, it is true that you'll be safe, but if one drive from each stripe set goes down, you will lose all your data.
So now that you have at least one backup copy of your data locally, what do you do in case of fire, flood, burglary, tornado, earthquake, sprinkler system, etc...?
Remote Backup keeps a copy of all your stuff on another PC somewhere far away from your main work. Running across town to your brother's place with a CD or DVD or hard disk of new stuff is also a pain. What's the solution? Using a geeky tool like rsync works very well, but there's a friendlier way. A service which keeps all your copies of all your files in sync all the time, automatically.
I'm sure there are others out there (and full disclosure, I also work for Microsoft), but consider the free service called FolderShare -
http://www.FolderShare.com. It will keep 2 (or more) computers in sync with one another over your network or over the internet. Works on both Mac and PC. It's a nice solution for lazy folks such as myself.
The only caveat is that there is a pretty serious limitation at the moment of 10 libraries (or top-level folders) with 10,000 files per library. Perhaps there are folks aware of other services which do the same thing without these limitations?
Murray, I can't help you much regarding keeping your originals vs. your .DNG's, because I have not used the Brumbaer software. I know that Adobe's DNG converter allows you to embed the original file in the DNG, to be safe, and that is a nice feature. But I don't think Adobe supports Sinar's file format yet.
Hope that helps,
-Brad