Tape Backup Rotation

A successful backup strategy protects data by ensuring there are adequate file versions available on tape and by keeping these tapes safe. There are a number of methods commonly used which we’ve summarised below.

FIVE/SIX/SEVEN-TAPE ROTATION

This is where you have a tape available for each day. They are labelled accordingly.

Tape 1 – Monday
Tape 2 – Tuesday
Tape 3 – Wednesday
Tape 4 – Thursday
Tape 5 – Friday

A slight variation on this is to add another tape into the mix – Friday 2 (Tape 6). You can then rotate the two Friday tapes so you get greater data protection. Storing one of the Friday tapes off-site each week provides further protection, for example against fire or theft. Using this method you would do incremental or differential backups for Monday through Thursday and then for Friday you would do a full backup.

The below chart shows how you might use this method in practice –

GRANDFATHER – FATHER – SON (GFS)

This is the one of the most commonly used rotation backup schedules. It is similar to the first example but includes more tapes in the rotation – 20. Daily tapes are known as SON tapes, Weekly tapes are known as FATHER tapes and Monthly tapes are known as GRANDFATHER tapes. You would label the tapes as follows –

The table below shows how you would use this method –

In this example, the month starts and finishes on a Friday. If this isn’t the case you would use the GRANDFATHER tape on the last day of the month and perform a full backup. Using this method you would also do an incremental or differential backup for Monday through Thursday and then for Friday you would do a full backup.

TOWER OF HANOI

This method is a secure and cost effective tape rotation schedule. It consists of 5 tapes in total which are labelled ? A, B, C, D, and E.

Tape A is used every second day.

Tape B is used every fourth day.
Tape C is used every eighth day.
Tape D is used every sixteenth day
Tape E is used every thirty second day.

So it should look a bit like this –

Using the above method you would do a full backup every time.

WHICH ROTATION IS BEST?

Now that you know 3 rotation methods, you need to decide which one is best for you. We have outlined the advantages and disadvantages for each method below.

SIX-TAPE – this is a great method as it only requires a few tapes. It is ideal for small data backups that fit on a single data tape. A major downside to this method is that it only keeps 1 weeks’ worth of backups unless you archive your tapes.

GFS – This provides the best data protection and security and implements monthly archival of tapes. It is a very simple but effective method and most software packages support it. The main drawback to using this method is that you require lots of tapes, which makes it expensive.

HANOI?- This is ideal for small businesses and is a more cost effective way by using fewer tapes than the GFS method. However this method isn’t straightforward to implement unless your backup software supports it and it can be hard to keep track of where you