David Magda
Guest
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 Posted:
Sat Feb 05, 2005 2:45 am Post subject:
Re: Tape Backup |
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Arno Wagner <me@privacy.net> writes:
| Quote: | 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.
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Any reason why three should be used?
--
David Magda <dmagda at ee.ryerson.ca>, http://www.magda.ca/
Because the innovator has for enemies all those who have done well under
the old conditions, and lukewarm defenders in those who may do well
under the new. -- Niccolo Machiavelli, _The Prince_, Chapter VI |
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Arno Wagner
Guest
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| Posted:
Sat Feb 05, 2005 6:07 am Post subject:
Re: Tape Backup |
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In comp.sys.ibm.pc.hardware.storage David Magda <dmagda+trace050112@ee.ryerson.ca> wrote:
| Quote: | Arno Wagner <me@privacy.net> 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?
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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
--
For email address: lastname AT tik DOT ee DOT ethz DOT ch
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"The more corrupt the state, the more numerous the laws" - Tacitus |
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Sayso Takewashi
Guest
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| Posted:
Sun Feb 06, 2005 12:43 am Post subject:
Re: Tape Backup |
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Arno Wagner wrote:
| Quote: |
I admit that you can work with 2 medium sets, if you get a
replacement
_immediately_ in case one of the media fails.
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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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