[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Edlug Archive Mar 2004 ]

Re: [edlug] DVD RW disks for backup - advice



Hi,

On Tue, 2004-03-16 at 22:57, A. Zelter wrote:
> I guess your right about the rm -rf, and indeed if someone hacked into a
> system that could happen, otherwise 'sitting on your hands' should prevent
> that. My criteria are different. I'm not worried about rm -rf, but
> that having to revert to yesterdays backup would cost me a day of data
> loss.

You're assuming that a bad sector is the only form of hardware failure
you care about.  That's just not true.  If you get a single bit
corruption somewhere, for example (could be a cable problem, a disk
problem, a CPU problem, bad cache memory or bad ram, or a plain overheat
due to a fan going bad) then that corruption gets written back to the
filesystem on both disks; and if it's in key metadata (an allocation
bitmap or an indirect block) then subsequent fs activity can corrupt
other files that you weren't even touching at the time.

And applications can have bugs which cause similar problems in their own
internal files.

"rm -rf" is just one trivial example of the sort of data loss that raid1
cannot help you with.  There are plenty of others.

Cheers,
 Stephen
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