[OpenAFS] vos shadow to backup user homes

[Harald Barth]

> However the main reason I'm replying is your comment about RAID. IMO,
> anytime you're configuring a mission-critical system without RAID
> you're probably asking for future headaches.

My experiences with RAID, especially HW-Raid is "mixed". Last week I
got an DL360 G4 with some built-in HW-RAID(5) that returned "read
errors" from the RAID to the OS without failing any drive(s). On an
email server. Looks to me like a serious bug in the RAID-firmware. I
even have found high-end RAID (Rio) whose memory did not deploy any
ECC. One device did make stripes of zeroes into every block that got
through it. Then there are HW-RAIDs which can detect silent bit-rot
on your HDs and some that can't. 

> All of my database and fileservers currently use hardware raid (3ware
> or LSI/PERC). But one of my "idle time" projects -- a bit of an inside
> joke since I have no idle time -- is to play around with ZFS on linux
> to see if I feel it's ready for prime time yet or not.

I currently trust linux SW RAID (MD) and ZFS more than any HW RAID. So
almost all our file servers have been migrated from HW-RAID to SW-RAID
or ZFS.

Plan is to complement that with shadow volumes for some volumes which
have data that need an way of "instant resore".

Harald.