This document discusses different tape rotation schemes for backing up data to tape drives. It describes the Grandfather-Father-Son (GFS), Tower of Hanoi, and Round Robin rotation methods. GFS uses daily, weekly, and monthly tapes to provide backups for up to a year. Tower of Hanoi uses a mathematical approach to optimize retention periods. Round Robin is the simplest but does not support long-term retention. The document recommends GFS for medium organizations and notes any backup system requires maintenance and testing.

1. TAPE
ROTATION
SCHEME
Presentation By : S.A Adewale Oloyi
Date : April 2015

2. TAPES
A tape is a storage device where information is stored on.
It’s an arguably better option to disk.
Why?
Life cycle
Durability
Ease of Use
Reliability
Disadvantage
Speed !!!
Uncertainty of data integrity
Shoe-Shinning Effect

3. Types Of Tapes
Tape Data Cartridge
Tape Cleaning Cartridge

4. HP MSL 8096
HP MSL 4048
HP MSL2024
Tape Library

5. Tape Library
IBM Tape Library

6. Dell PowerVault
TL4000
Tape Library
Dell PowerVault
TL2000

7. Tape Backup Technology
 LTO3
 LTO4
 LTO5
 LTO6
Linear Tape-Open (or LTO)

8. Tape Management
Tapes have a long life cycle and durability
nonetheless, they should still be managed
appropriately for the sake of its contents-
Hence, an effective management policy
How?
By rotating the tapes

9. Tape Rotation Strategy
Things to consider
 R.P.O (Recovery point Objective)
 Number of Tapes Available
 Off-site Storage
 Retention

10. Strategies
For this presentation, 3 strategies will
be discussed.
 G.F.S (Grandfather- Father- Son)
 Tower of Hanoi
 Round Robin

11. G.F.S Tape Rotation Scheme
This is an explanation of the industry-
standard Grandfather-Father-Son tape
rotation schedule.
This backup schedule is appropriate for
most small businesses.
It is a compromise of protection,
convenience and performance

12. The total number of tapes you will require is based
on your desired "restore window". A typical business
with a 5-day work week will use a 20-tape rotation that
will give them a one-year restore window.
Many, if not most businesses will also keep yearly tapes
which can come in handy for tax reporting purposes.
For a 6-day work week ,you will need 22 tapes.
This will allow you to restore files as recent as yesterday
and as old as one year.
A 6-month restore window requires 14 tapes
Number of Tapes Required

13. Tape Labels
Daily Tapes
4 tapes will be used every Monday through Thursday.
These tapes will be used every week and will experience the
most wear and tear.
It is recommended the daily tapes be shifted to the
monthly group once in a while so they don't wear out
prematurely...like rotating the tires on your car.
Monday
Tuesday
Wednesday
Thursday

14. Tape Labels
Weekly Tapes
4 more of your tapes will be used once a month on
Fridays. (or Saturdays, depending on whether or not you
are backing up a six-day workweek).
Whenever it appears you need a Friday Week 5 tape,
you should just use the EOM (End of Month) tape.
Friday Week 1
Friday Week 2
Friday Week 3
Friday Week 4

15. Tape Labels
Monthly Tapes
Twelve of your tapes will be used
on the last business day of each
month.
 January EOM
 February EOM
 March EOM etc

16. Quantity of Tapes
Daily Tapes + Weekly Tapes + Monthly Tapes
4 + 4 + 12
Total = 20 Tapes
A 5-day work week = 20 Tapes
A 6-day work week = 22 Tapes
Daily Tapes + Weekly Tapes + Monthly Tapes
5 + 5 + 12
Total = 22 Tapes

17. Tower of Hanoi

18. The Tower of Hanoi rotation schedule is widely used.
This schedule can be used in either a daily or weekly
rotation scheme. The decision regarding the frequency of
rotation should be based on the volume of data traffic. To
maintain the required history of file versions, a minimum
of 5 tape sets should be used in the weekly rotation
schedule, or 8 for a daily rotation scheme.
. As with the G.F.S rotation scheme, tapes should be
periodically removed from the rotation for archive
purposes.
Tower of Hanoi

19. Tower of Hanoi
The Tower of Hanoi rotation method is more
complex.
It is based on the mathematics of the Tower
of Hanoi , using a recursive method to optimize
the back-up cycle.
So the 1st tape is used every other day
(1, 3, 5, 7, 9,...),
the 2nd tape is used every 4th day (2, 6, 10, ...),
the 3rd tape is used every 8th day (4, 12, 20, ...).

20. Tower of Hanoi
A set of n tapes (or other media) will allow
backups for 2 ^n-1 days before the last set
is recycled. So, 3 tapes will give 4 days'
worth of backups and on the 5th day it will
be overwritten; 4 tapes will give 8 days, and
it is overwritten on the 9th day; 5 tapes will
give 16 days, etc. Files can be restored
from 1, 2, 4, 8, 16, ..., 2 ^n-1 days ago.

21. Tower of Hanoi

22. Tower of Hanoi
N= NUMBER
OF TAPES
WORTH OF
BACKUP IN
DAYS
2** (N-1)
N=3 4 DAYS
N = 4 8 DAYS
N = 5 16 DAYS
N = 6 32 DAYS
N= NUMBER
OF TAPES
WORTH OF
RETENTION
IN DAYS
(2**N) -1
N=3 7 DAYS
N = 4 15 DAYS
N = 5 31 DAYS
N = 6 63 DAYS

23. Tower of Hanoi
In this method, a set of numbered media is
used until the end of the cycle. Then the
cycle is repeated using media numbered the
same as the previous cycle, but incremented
by one. The lowest numbered tape from the
previous cycle is retired and kept
permanently. Thus, one has access to every
backup for one cycle, and one backup per
cycle before that.

24. Tower of Hanoi
1ST CYCLE 2ND CYCLE 3RD CYCLE 4TH CYCLE
TAPE 1 TAPE 2 TAPE 3 TAPE 4
TAPE 2 TAPE 3 TAPE 4 TAPE 5
TAPE 1 TAPE 2 TAPE 3 TAPE 4
TAPE 3 TAPE 4 TAPE 5 TAPE 6
TAPE 1 TAPE 2 TAPE 3 TAPE 4
TAPE 2 TAPE 3 TAPE 4 TAPE 5
TAPE 1 TAPE 2 TAPE 3 TAPE 4
TAPE 3 TAPE 4 TAPE 5 TAPE 6

25. Observation
As you can see, the lower numbered
tapes get used far more frequently than
higher numbered tapes. This means that
the Tower of Hanoi scheme won't retain
daily backups for a week like the other
tape rotation schemes, but it does give you
exponential retention periods.

26. Observation
For example, in the 5 tape rotation scheme,
Tape 1 is used 16 times (every other day).
Tape 2 is used 8 times (every 4 days).
Tape 3 is used 4 times (with 7 days in between).
Tapes 4 and Tapes 5 are each used 2 times.
In essence, this gives you daily and monthly
backups like the other tape rotation schemes do,
but you use far fewer tapes in the long run.

27. Disadvantages of Tower of Hanoi
The downside to this rotation scheme is its
complexity and the fact that not all backup
applications support it.
This method also has a tendency to wear out lower
numbered tapes because they are used so much
more frequently than higher numbered tapes.
Another disadvantage of the method is that
(short retention period)
half the backups are overwritten after only
2 days.

28. Round Robin
Round-Robin is the simplest of tape rotations to
understand. This type of cycle uses a single tape
set for a set period of time, but only keeps the
information for the length of that time period.
However, it forces the Administrator to frequently
re-use the tapes over and over again.
Due to wear and tear, these tapes would be
replace frequently. Another con to this type of
rotation is that there is no long-term storage
solution.

29. Round Robin
Example: A weekly Round-Robin tape rotation
would mean that there are tapes marked
"Monday", "Tuesday", "Wednesday", etc.
Each day’s tapes are used on that specified day
of the week, and then re-used 7 days later

30. Round Robin
One other simple scheme is to have 5 backup tapes
(one for each day of the work week) and to use each
one in succession. This way, you use the same tape
every day of the week. For extra protection, you can
use more than one tape for one day of the week, say
Friday, and rotate the Friday tape offsite every week.
This system pretty much requires that you do a
full backup every day. This may be fine for a small
business without a lot of data to preserve, but it can
mean a good-sized backup window every day.

31. Limitations of Round Robin
The biggest problem with the Round Robin variations
is that it doesn’t support long-term data retention,
which is very important to have in a data backup plan.
To see why this is important, imagine that an
organization uses a 4-week tape rotation scheme.
Now suppose that an organization finds that a critical file
has been corrupted. If the corruption occurred more
than four weeks ago, then there are no good copies of
the file that can be retrieved from backup.
For this reason, most of the organizations that use
Round Robin also use data archiving.

32. Recommendations: Small organizations
There are many small organizations who can fit all of
their data files onto a single tape. Since backing up this
small amount of data does not take much time, many
small organizations prefer to do full backups on a daily
basis, and to rotate their tapes in a round-robin strategy.
Assuming there are no actual IT personnel staffed by
the company, this method of daily full backups puts
everyone’s mind at ease and does not require a large
collection of tapes. However, keep a couple of spare
tapes on-hand in the event one of them breaks.

33. Recommendations: Medium organizations
Companies of this size usually prefer to implement a G.F.S
rotation method. Since this size of organization probably
has a small IT staff, they should all be made aware of how
the backup jobs and tape rotations are implemented. To
prevent confusion, the dates of the backups and their
associated tapes should be documented for future
reference. The actual backup methods depends on your
needs, but a minimum of the following is recommend…
Monthly Full backups, Weekly Incremental backups, and
Daily Differential backups.

34. Recommendations: Large organizations
It is assumed that large organizations will have a large
IT staff. Backup Administrators will be responsible for
managing to a large amount of data which will no doubt
be changing very fast. To that end, they will most likely
prefer to tighten up the backup jobs to require
Differential backups to be performed every couple of
hours, Incremental backups every evening, and Full
backups a minimum of once per week. The tape rotation
would also be at the Backup Administrators discretion.

35. Note that any backup system absolutely depends on
daily attention and periodic maintenance.
Every backup system requires a "backup
administrator" to change the tapes every day, to store
them in the proper location and to monitor the backup
logs for any errors.
Periodically, every backup system needs to be tested
in order to be sure data is actually being backed up and
can be restored when needed. Tape drives also need to
be periodically cleaned. With most tape drives, this
generally means occasionally inserting a cleaning tape.
Reliability

36. In the end, there is no one single backup tape
rotation scheme that is clearly superior.
Each tape data backup scheme has inherent
advantages and disadvantages. It is ultimately
up to you to choose the scheme that is the best
fit for your organization's needs.
Conclusion

37. THANK
YOU
FOR
LISTENING!