King Nobby wrote:
We use RAID1 and RAID6...
Neither of which are RAID0. ;)
RAID0 is simple concatenation of filesystems. So you take two drives and make them look like one drive to your operating system. Great! Until one of the drives fails.
The only reason to do this is to use striping to do faster data writes across more heads with the lowest total overhead. The trade off is a massively higher risk of failure. If one disk fails, the entire "drive" is lost (and by "drive" I mean all the drives included in the RAID0 device since the OS sees them all as one filesystem). Gone. Poof! Hope you got a backup...
It's popular for home users I suspect almost entirely because most home users don't actually know how stupid it is to use it. A mainboard manufacturer can bundle in a RAID0 package and sell it for a bit more then a board without, and users assume that since they paid extra for the RAID package that it must be a good thing to do. It's a great example of self created marketing.
Other RAID levels have uses, but IMO not much for home use. All of them cause a performance hit and loss of total disk space (except RAID0, but that's a disaster waiting to happen). Those are all things the typical home user wants to avoid. That's not to say that setting up a RAID5 array for storing massive amounts of mp3 files isn't something a home user might be interested in, but I'd do that by actually buying an external array designed for that, not by utilizing the relatively crappy onboard RAID systems.
For the record, I'm also not to thrilled with RAID6 systems either. It just seems like a paranoid over expense for what you get. IMHO, you are vastly better buying a high quality file server solution then doing this. We've been using NetApp filers for over a decade (which actually uses a customized version of RAID4, so go figure!). In that time we have *never* lost a single piece of data due to a disk failure. That's not to say that disks haven't failed, but that the systems are designed to make a double disk failure virtually unheard of (Hasn't happened).
RAID6 is essentially mirrored RAID5. RAID5 only fails if you lose two disks at the same time (two disks within the same raid group technically). As I stated above, if you go with a solid performer your odds of this happening are virtually zero. More to the point, RAID6 will still fail if you experience a "double double" disk failure (two disks on the primary and two on the mirror all die before you can recover). When you start narrowing down the odds of a single double disk failure occurring, you're down so low that you're hitting the odds of say a building fire, natural disaster, or crazed worker destroying your filer being more likely. Adding mirroring is protecting against a case that's ridiculously unlikely to happen, but literally doubles the total cost of the solution.
But hey. Some admins are a bit crazy about stuff like that...