Veritas-bu

Re: [Veritas-bu] Media Tape Writes and Retentions

2009-02-18 12:24:04
Subject: Re: [Veritas-bu] Media Tape Writes and Retentions
From: <judy_hinchcliffe AT administaff DOT com>
To: <c-todd.jackson AT invitrogen DOT com>, <veritas-bu AT mailman.eng.auburn DOT edu>
Date: Wed, 18 Feb 2009 11:03:09 -0600

I should clairfi this part

now you have   blankspace, week2image, week3i mage, week4image

 

it is not really a blankspace – it is an expired image. (the info on the tape does not get erased).

You could still import the tape and get back week1image if needed.

 


From: Jackson, Todd [mailto:c-todd.jackson AT invitrogen DOT com]
Sent: Wednesday, February 18, 2009 10:59 AM
To: Judy Hinchcliffe; veritas-bu AT mailman.eng.auburn DOT edu
Subject: RE: [Veritas-bu] Media Tape Writes and Retentions

 

HI Judy

 

Thank you for your reply

 

Yes I was referring to IMAGES and not actual TAPE but was careless in my general terminology.

I have no plans on mixing retentions or leaving a media tape in the Library after it has been assigned.

We have some new policies for offsite retentions and I just wanted to throw out a spare of the moment scenario to gather some information.

 

Everything you sent was Extremely helpful and very informative and I thank you for taking to time to

explain. There were some things that I did not know that you have cleared up.

 

 

Thanks

-T

 

 


From: judy_hinchcliffe AT administaff DOT com [mailto:judy_hinchcliffe AT administaff DOT com]
Sent: Wednesday, February 18, 2009 11:43 AM
To: Jackson, Todd; veritas-bu AT mailman.eng.auburn DOT edu
Subject: RE: [Veritas-bu] Media Tape Writes and Retentions

 

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

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