>Hi. In my research group, we back up as frequently as we can, but still
>run into problems because of the unreliability of our backups. We use
>an Exabyte 8200 8mm drive. We go through 8mm tapes like crazy, because
>they keep dying with media errors after minimal use.
The Exabyte 8200 drives are less reliable than the Exabyte 8500 drives;
you might want to consider upgrading. Also, in my experience "media
error" can indicate drive problems. Since Exabyte drives are repackaged
and sold by everyone from here to Lower Slobovia, vendor quality, and
drive packaging quality, varies greatly. Another cause of bogus medua
errors, which can lead to the problems you describe, is mentioned below.
An example of vendor quality problems: one 8mm reseller - who fixed
this problem very quickly once they realized they had it - set up their
drives so that the fans sucked air over the tape heads, resulting in
great big * dust bunnies that caused monstrous grief. They fixed
this problem so that the dust was expelled instead of sucked in.
Note that if "media errors" continue, you will likely start getting
hardware errors. This is due to the "flaking scum" described below.
Once you get hardware errors, your heads will need replacing.
Quote:>We use pre*ly Maxell and Fuji (112m length) tapes, because that's what
>we can get from University Stores or local vendors. But quite frequently,
You might want to try the Exabyte "DATA" grade tapes. These are tapes
manufactured by Sony and "data certified". DATA tapes are more
expensive than most others, but they are worth it: they cause less head
wear and generate fewer errors.
When I looked into DATA tapes, it took me months to get a clear and
cogent story on data certification, and what it boils down to is this:
1) The tapes are cut from the center of the wide swath of tape
material, meaning there is less chance of tension-related
degradation of tape quality during the manufacturing process.
2) More importantly, the tapes are tested before being packaged and
shipped.
Point (2) is important for non-obvious reasons. The first time an 8mm
tape is used, it "flakes" material on your tape heads. These deposits
wear at the heads, reducing their lifetime. This can contribute greatly
to drive quality problems, and to "media errors".
With non-DATA tapes, their first use is the first time you back
something up to them. This means that if you buy a batch on new
non-DATA tapes, you quickly cause scum buildup on the tape heads. This
can cause tapes written later in the backup cycle to be unreadable.
The advantage of the DATA tapes is that they deposit this scum on
someone else's heads. Your first use of the tape is the tape's second
use (at least); the much cleaner tape leaves less scum on the heads.
Note that this scum cannot be removed from the heads with cleaning
cartridges: you must swab the heads with a special (isopropyl ??)
solution. Note that there are two versions of the tape head cleaning
solution: one is a carcinogenic CFC, and the other is a relatively
non-toxic, safe, solution. (We had to investigate the latter as
Northern Telecom, BNR's parent, has very strict chemical use and
environmental policies which prohibit the use of CFCs in company
operations.)
In any case, you should use Exabyte 12 pass cleaning cartridges
regularly (we back up to EXB-8500s six nights a week - that's
4GB+ a night - and clean the drives once a week), and have your
service supplier clean the heads with the aforementioned solution
on a regular basis (I don't remember off-hand how often we do this here;
every six or twelve months comes to mind).
Before we began a regular cleaning regimen and switched to EXB-8500s and
DATA tapes, we had many "media errors" (which eventually resulted in
hardware errors); now we have almost none.
Final note on cleaning: never use camcorder head cleaners, they will
destroy your heads, and probably void your warranty (if your supplier
has any brains).
pww
--
Peter Whittaker [~~~~~~~~~~~~~~~~~~~~~~~~~~] NT Secure Networks
Ph: +1 613 765 2064 [ ] Ottawa
FAX:+1 613 765 3520 [__________________________] K1Y 4H7
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