1) The IMAGE has the 5 week retention not
the tape.
a. Is if you write to the same tape 3 weeks
in a row the tape will not become scratch until the oldest images on the tape
expires (week 3’s image date + 5 weeks)
2) no
a. when writing to a tape it will only
append to the end of the tape, past the last written image to the tape
b. so if you have week1image,
week2image,week3image, week4image
c. and
^^^^^ week1 expires
d. now you have blankspace,
week2image, week3i mage, week4image
e. and you write to the same tape again you
get
f.
blankspace,
week2image, week3image, week4image, week5image (tape is now full) (will not become
scratch until week5’s image expires)
3) if the tape has no assigned time then it
is a scratch, no valid images on it
a. if the tape is in the library and in a
pool that your policy can use or the scratch pool it can be written to.
b. If you leave the tape in the library your
backups will continue to write to the tape until it is FULL
c. If the tape becomes FULL meaning that it
has written all the way to the EOT it will NOT write to again until all images
on the tape have expired (see #2)
d. If you do not allow different retention levels
on the same tape – say mixing of 5 week retention and 6 month retention,
then it will choose a different tape for the 6 month retention.
4) As the first image is written to the tape
it gets an assigned date. On the second day when it writes to the tape it
will not change the assigned date, but it will change the expiration date (as
the expiration date is based on when the last image on the tape will expire and
the tape becomes scratch.)
In my
production environment we remove the tapes from the library every morning and
send them off site. So my assigned time on my tape represents when my
backups were done, because I do NOT put more then one days backup on a tape (
what if the tape went bad and I could not read it, I could loose days of data.
I do not mix
retention periods on my tape because I could have just 1 gig of data on a tape
with a 6 month retention and 400 gig of 2 week retention. That tape does
not become scratch again until the 6 months have passed.
From:
veritas-bu-bounces AT mailman.eng.auburn DOT edu
[mailto:veritas-bu-bounces AT mailman.eng.auburn DOT edu] On Behalf Of Jackson, Todd
Sent: Wednesday, February 18, 2009
10:18 AM
To:
veritas-bu AT mailman.eng.auburn DOT edu
Subject: [Veritas-bu] Media Tape
Writes and Retentions
Hello All,
I have a question concerning LTO tape writes that I need
some clarity about.
Scenario:
If you have a Retention of 5 weeks for a policy and you
write a job the first day which gives the
Images 5 weeks until expiration. When you write to that tape
again on week 2, week 3 … etc.
My question are
1) Will each week of writes have a separate 5 week
retention?
2) Can the tape be written to again (over week 1 space on
tape) by week 6 or will something else happen?
3) When the time is unassigned I am assuming that is all
backup images expiring. Will the tape be written to as
long as it is in a Library or drive and not write protected
.. every time a segment of images expire on the tape?
4) When that happens how does the time assigned change? Will
it keep the initial time assigned or change to the
Latest time assigned image?
LTO MEDIA TAPE USAGE
| Week 1, Write job |
Week 2, Write job | Week 3, write
job | Week 4, write
job | Week 5, write job
Any other information is appreciated concerning how this
works.
Thanks
-T