Correct.

Raid 1+5 = 15

 

that's happened to me before...one drive failed, then while the replacement was being delivered to the colo another failed and it was lost.

 

I don't know of too many backup admins backing up OS and it's sub-directories. It's more common and also more cost effective to have ghost images for your servers.

I just can't justify the costs associated with Raid 10. I guess if you are looking at all out performance and money is not an issue this is the solution. I have yet to work for a company that had this philosophy however . It provides the same level of fault tolerance as Raid 1 and not to mention the same overhead for fault tolerance as mirroring.

As for Raid 15 or Raid 51, with storage affiance ranging in 30-40% I just can't imaging most companies (well at least mine) approving this. There are other efficient and easier methods to providing fault tolerance. Clustering comes to mind.

 

You are right as far as NT servers are concern. But if you were to expand your definition of server beyond Microsoft products, you will realize that Norton Ghost does not go there... What I mean is all OS related files such as user profiles, etc...

I agree with your comment on RAID 15.

 

I have to be reminded constantly about the other OSs out on the market . I can't agree with you more about testing backup tapes on a routine basis. I got burned pretty bad once when I popped in a tape only to realize that the files I needed could not be restored .