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Tape Backup



 
 
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  #61  
Old February 5th 05, 02:07 AM
Arno Wagner
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In comp.sys.ibm.pc.hardware.storage David Magda wrote:
Arno Wagner writes:


Good idea. This is really just "persistent buffering", a quite old
technology, e.g. implemented in many tape-library storage systems.

But please use at least 3 independent sets of tapes with this too
and verify the readability of your tapes at regular intervals.


Any reason why three should be used?


2 is simple:
While you do a backup, you destroy one. So if
you discover a problem with the original while making a backup,
and you have only one medium, you are entirely without backup _and_
have a damaged original.

My personal reasons for 3:
- If you only have 2 and then one of the media dies,
you run into the problem above.
- It adds some redundandency. 2 is clearly the minimum. So 3
adds a safety margin, i.e. when one medium dies you can still
an additional backup.
- If you backup device/software breaks and kills the medium
(for whatever reason, can also be a virus, etc.), you
are likely to assume medium failure first and try with
the second medium. If that breaks also, you still have one
good backup.
- Other good reasons I am not aware of. It seems to be common
wisdom among sysadmins...

Actually many admins think that 3 backups are too little, because
you get too little history. Still, better any backup than none,
but don't feel to safe even with backup.

I admit that you can work with 2 medium sets, if you get a replacement
_immediately_ in case one of the media fails.

Arno

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  #62  
Old February 5th 05, 08:43 PM
Sayso Takewashi
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Arno Wagner wrote:



I admit that you can work with 2 medium sets, if you get a

replacement
_immediately_ in case one of the media fails.


Since 2 Days i use a DLT to save Backup Images to Tapes.Currently,i
have 5 Sets of different Days on it.
Why 5 Sets?
I make them over the time and store them on 3 different Hardisks.But
they are full now and i have to store them elsewhere.And with 70 Bucks
for a used Dlt and 5$/Tape,the Cost Issue Disk vs. DLT are no longer
valid.The Software i use,is the "famous" Tar from a Linux CD.Why
Tar?It just works as it should and no need for a 70$ Backup Software.

 




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