Cheapest way to backup data

[Richard Pieri]

On Feb 22, 2009, at 12:30 PM, 100ji wrote:
> Hmm, is this the property of all raid levels though? What about raid  
> 6 where
> there is a parity bit set which can be used to recover the data? I  
> read some
> pages on raid and I am unable to confirm that RAID only provides data
> integrity. Probably the performance sucks, but that's a trade off.

If you delete files from a RAID then those files are gone.  RAID  
redundancy does not provide for recovery of the data.  The disks --  
the media -- are fine but the data is gone.

If you unplug a disk from a RAID then the RAID redundancy keeps things  
running until you replace that disk.  Your data remains intact because  
of the redundancy of the underlying media.

See the difference?

> Doesn't the data integrity depend on the software we use?
> For example, can't the software we use ensure that the data is  
> redundant
> enough that I can recover the whole data even if say 25% of the my  
> data is
> lost? Isn't there such a software?

There probably is, but that isn't a backup.  It won't provide recovery  
after a total loss.