indefinately.  When we start seeing a lot of read errors, then we freeze the tape and then properly dispose of it during the next vaulting session.

It is impossible to say.

Some comapanies use tapes as the post above, untill they have issues, for some this is too late.  You need to consider that the time you start having issues could be an important restore !  In defence of the above post however, it is harder for a drive to write to a tape than read it (needs more signal strength) so a worn tape/ drive I would expect to see write errors before read, however this is not 100% certain.

A general rule of thumb, is that companies replace 100% of media every 3 years, again, this would depend on the number of media you have.

Strangely enough, I mentioned a 3rd party product call StorSentry on a previous post today, this is a piece of software that uses statistics and scsi errors direct from the drive to monitor tape and drive health.

To save me writing 5 pages, I've used it, I've seen it used in a big environment and yes it works, in my opinion very very well.  It's marketed by Imation, but written by a company called Hi-Stor. (before anyone asks, I have no links  to either of these companies).

About a year or so after it was released, it was in about 42 companies in the uk, and it was found, that of the tapes people though needed replacing, only between 3-4% actually did, so it would actually pay for itself within a 3 year period, if of course the tapes are in good condition.

The condition of the drives, and manufacturer of the tapes all play a part as to how long a tape will last - for example shoe-shining will reduce the life of a tape and the drive by an amount which could be a little, or it could be a lot, again, impossible to say. 

Another big factor is if the tapes are transported offsite.  Often tapes are incorrectly transported, or at least not transported as well as they could be, which may have a  factor in reducing life, although this does tend to be "instant" failure.  For various reasons, tapes that undergo show-shing are particularly at risk when moved.

Also, sometimes the number of passes is quoted as a limiting factor by the manufacturers.  For an LTO tape, for example, if you  write it till it is full, it will have made multiple passes over the heads of the drive, as the centre tracks are written first, then when the end of the tape is reached, the heads then read the next tracks out and the tape is written in the reverse direction, this repeats until the tracks on the outer edges of the tapes are written.   Therefore, if you write your tapes until full, then the no. of passes is not equal to the number of times the tapes has been written until it was full.

Hope this helps,

Martin

all tapes written to eventually go offsite for very long term retention, so there is only a small window of constant use for our tapes. 

If you are in an environment where you will be using tapes until they wear out, then yes, I would say to have some replacement plan after so long.  Some will also say that a regular drive cleaning schedule will prolong the life of a drive as well as the life of tapes.

Fine post mph999

I would like to turn around the picture a little by asking how long is you're shortest retention level ?

A media format become obsolete in 4 years.  But even with a very short retention of , let's say one week, it still only 208 usages in 4 years. That's well below the 20.000 load/unload cycles Imation claim they support.

If media causes trouble, discard them. Life if to short for media trouble, but check the reliability tape drives too !!!.

Thank you.

Well, back at the environment I was refering to, the shortest retention was 1 week, we had around 25000 media, 460 physical drives and backed up around 60-70 TB a day, most to tape.  Actually, all to tape, though a little went via VTL etc ...

Also, don't forget the manufactures claims will be in a drive in a lab, the drive will be in tip-top condition and the air as clean as you can get.

You are correct with the number of uses, it very diifficult to get anywhere near the claimed.  However, having spent quite a long time looking specifically at drive/ media issues, it is not unreasonable to say, that the number of mounts is irrelvant.  The treament of the tapes, shoe-shining, transportation (vaulting) , condiions kept in etc ... outweigh the effect of the number of mount cycles the media has undergone.

Martin

Nicolai

20.000 load/unload cycles - thats rather a lot.
where did you find that specification?
i can only find a archival term spec of 30 years for a sdlt320.

Martin

Your StorSentry & Imation tape comments were in my other posting today, in reponse to specific issues with 1 of our sites. I will certainly look at StorSentry.

This post was a more general question, to come up with an IT Policy on tape replacement across all of our sites.

Thanks for the input, its interesting to hear the different approaches.

Take a look at this topic at Wikipedia http://en.wikipedia.org/wiki/Linear_Tape-Open

There are some starts regarding LTO tapes lifecycle.