Re: number of global spares?

On Sat, 2005-08-27 at 15:00 +1000, Daniel Pittman wrote:

"Guy" [off-list ref] writes:

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I've been working on a RAID setup with dual RAID controllers and
three expansion boxes - 48 disks in all, including data, parity and
global spares.

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They don't feel that the storage has to be blazing fast, and 100% uptime
isn't paramount, however they very much do not want to lose their data.

The filesystem will not be backed up - we simply don't have anything large
enough to back it up -to-, so if the some part of the storage solution
goes kerflooey, we're totally...  er...  out of luck, and they'll probably
be looking at me (the primary sysadmin on the storage configuration),
wondering why their data is gone.

RAID5, 6 or 1 is not data backup!  It is hardware redundancy!!
Data loss or corruption can still occur with a RAID solution.  RAID won't
help if someone fat fingers a "rm" command.
Corruption of the filesystem can also cause major data loss, without a
failed disk.

If the data was lost, what would it cost to re-create it?
Enough to buy a backup system?

I absolutely agree with this.  When - and it is when, not if - the
content of this filesystem goes away, you will be rightly blamed for it.

Invest the few thousand dollars in a good high capacity tape drive and
pay someone to change the tapes.  This will be worth it when the system
finally does fail in some nasty, unpredictable way!

I was on paternity leave when the solution was selected, but the guy
with the grant money has been disinterested in backups from the
beginning.

The policy is going to be "your homedir will be backed up.  Your files
under /data will not, unless you back them up yourself."

My job is to work within that restriction, and possibly advise for
backups, but nothing more.  The purchasing decision is not mine.