SUMMARY: scheme to recycle dump tapes

From: Zina Yung (
Date: Fri Mar 31 1995 - 03:35:32 CST

Hello SUN managers:

My original posting:

Hello SUN managers,

We keep the full image of our file system at the beginning of each
month for as long as we can remember. I wonder how many full dumps
that you keep and what kind of recycling strategy you use in your

Have you heard anything about the exponential decay algorithm?

We'll post a summary. Thanks very much.

My summary:

Other sites keep their full dump tapes ranging from 6 months to
a years, depending on the type of data. Some important legal data
will never recycled, system files will be kept longer than user files.

I would like to thank every one who responded to my question.
The following are schemes/comments that may be of interest to others:

1. Seven sets of tapes: week1, week2, week3, month1, month2, quarter1,
   and quarter2 ... Depending on your needs you can take a new set
   of tapes each time you arrive to "q2", saving the old one forever.
   Thanks to Alex Pokras <>

2. We keep ~12 weeks of daily backups before we start recycling tapes.
   At that point we archive one tape per week (usually monday) and place
   alternate weeks off site.
   Thanks to (Robert D. Worsham)

3. we make a back up in the early morning on the 1st day of every month,
   and we keep those tapes for a long long time... (we have never
   recycled these tapes)
   Thanks to (Derald McMillan)

4. Monthly full dump of system files - kept for 1 year;
   Monthly full dump of user files - kept for 6 months (this was typically
          the first weekly dump of the month)
   Weekly full dump of user files - kept for 6 weeks
   Thanks to "Susan M. Menig" <ddq251f@shoes.Bell-Atl.Com

5. Data tapes 8-mm should be used no more than 35 times
                3M and Basf recommendations.
   Thanks to jcsadmin! (John Ciesla)

7. Legal requirements notwithstanding (we have some Federal customers who
   want everything retained forever) we keep monthly image dumps for three
   years, then recycle
   Thanks to

7. I dump every machine completely twice a week on a set of 8 Exabyte
   tapes I use. Then, once a month, I do a monthly dump once a month
   on a set of 6 tapes. Every six months, I make a permanent archive and
   never use it again.
   Thanks to Nico Garcia (


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