why clean tape drives more than once

[John Bolene]

JRF fixed my make_recovery problem but I had just cleaned the drive before the backup.

He suggested I clean it again and that worked.

Why would it need cleaning more than once as it only gets used 2 or 3 times a month?

What does that silly tape cleaner tape actually do as it looks like an ordinary tape?

[James R. Ferguson · Accepted solution]

Hi John:

OK. The cleaning tape is designed to pass forward only once -- just like a rag that you would wipe across something and throw away. Each time you use the cleaning tape a fraction of the extent passes over the tape heads to remove bits of crud and oxide.

If you have a very dirty tape drive, multiple "swipes" may be necessary to clean it.

Very dirty tape drives start with old tapes that deposit oxide on the heads. Hence, replace your tapes after long periods of usage. Practice "safe tape sex". Inserting old, worn tapes into a drive may deposit material that is then picked up by new tapes.

Regards!

...JRF...

[Paula J Frazer-Campbell]

Hi

Tape drives -DDS should be cleaned after approx 20 hours.

My backups take circa 3.5 hours so approx 6 backups = 20 hours - hence clean at least once a week.

HTH

Paula

[Bernie Vande Griend]

Good question. I've run into this on SUN equipment as well.
3 things come to mind:
1) The tape is supposed to clean the head on the tape drive, but if it is really dirty, the normal cycle for one cleaning may not be enough
2) Its possible for the head to become dirty even with just one tape.
3) They just don't make these stupid tape cleaners very well, and it may not have done anything the first time.

[Jay Newman]

The answer to both your questions relies a bit on what kind of tape drive you are using.
However, in general, tape drives gradually build up residue on the read and write heads, which causes all sorts of problems with backups.
If you put a reasonably "clean" tape (no noticeable amount of dust etc.) into a dirty drive, chances are you will transfer some residue back onto the tape.
After you clean the drive, putting a dirty tape back in could just gum it up again.

As for what those cleaning tapes do, they are supposed to gently rub any residue off of the heads. Since it is done gently to avoid abrasion to the surface of the read and write heads, you sometimes have to retry it.
Think of it as cleaning the kitchen counter with a soft cloth.. every now and then something is a bit stubborn and needs a bit of extra effort to be removed.
By the way, some tape drives do not have doors that properly close when not in use. Then you can build up dust etc. from the room without even inserting a tape.
Many of our users leave a tape inserted in the drive all the time, so that there is much less risk of contamination from outside.