ken@rochester.UUCP (03/28/87)
Ok, I got a couple more responses to my request for tape ratings. I've
decided to post what I have. But I'm still taking mail. Thanks to all
who responded.
Ken
From: cmcl2!phri!roy (Roy Smith)
We use almost exclusively BASF Endura. I'm not much of a magtape
guru; we use it because it's relatively inexpensive and that's what our
major supplier stocks. We used to use unbranded tape, i.e. Pryor's own
brand which I'm told (by the sales rep) was manufactured by Wabash, but
we've sworn off that. For the past few years we've been doing 1600 on a
DEC TU-80; about 9 months ago we got our Suns and now do both 1600 and 6250
on their drive (a Fuji something-or-other). The TU-80 still gets daily use
for dumps on the VAX. We've used 600, 1200, and 2400 foot reels for the
past several years. Recently they started making BASF Endura in 300 foot
reels (same reel as a 600 foot tape, but half empty) and we bought a few
boxes of that to see how it works out.
How well you maintain your drive is probably a big factor. We're
kind of lax on that, but I clean off the heads and rollers on both drives
occasionally; maybe every other month or so. We should probably do it more
often, but I figure every time I pull the cover off the heads to get at
them with a swap, that's one more chance to scratch them or something.
So far, no complaints. We had some bad experiences when our TU-80
was new (getting write errors a few hundred feet into the tape and/or
running off the beginning or end of the reel, past the EOT marker) with the
BASF Endura, but I'm almost certain the fault was not in the tape but in
the drive (DEC changed a board and the problem went away). I've got one
level-0 dump which I can't read (on Endura), but that was made years ago
when the TU-80 was new; it may very well have been either due to the drive
or even operator error (we were new to 4.2 and dump then). Actually, the
most recent bad thing I had happen to a tape was when I dropped it on the
floor and broke the plastic reel. Good thing it was a new tape and didn't
have anything on it. I'm curious about mechanical shocks and magtapes, but
not willing to experiment with *my* data!
We've been using the same set of 10 2400 foot tapes for daily dumps
on the TU-80 for must be 3 years now. Figure each tape gets used about
once every other week, so we're talking 75 passes through the machine for
each tape. Of course, most of the tape doesn't get used, but the beginning
of it does every time, and we havn't seen any problems. We use the same
stuff for archival level-0 dumps too. We randomly pick a virgin tape, or
if I've got some tapes that I don't need anymore, I use those. Most of the
archival dumps never get looked at, so I don't actually know if they are
readable, but on the occasions when I've needed to go back to old dumps,
I've never had any problems (except for the one mentioned above).
The bottom line, in my opinion, is that as long as you buy a name
brand tape, you don't have to go ape-shit to get the absolute best quality
you can buy. But, like I said, I'm not a tape expert. The only rule I
obey without fail is that I *never* use a tape until it's had a chance to
come up to room temperature, no matter how desperate I am for that new
shipment. In the winter, those tapes are pretty damn frigid when they come
off the truck (but why am I telling somebody in Rochester about winter?)
Roy Smith, {allegra,cmcl2,philabs}!phri!roy
From: [someone who prefers to be unnamed - Ken]
Manufacturer: Memorex
Brand: MRX IV
Density you use: 1600 60% 6250 40%
Tape length: 2400, or is it 3200?
Comments: Very good price wise, but it seems to have have problems
after about 40 reads/writes then gets progressivly worse. 7/10
frequency: daily 10%
weekly backups 60%
file transfers 5%
archivals 25%
From: "Wombat" <rutgers!pur-ee!j.cc.purdue.edu!rsk>
Manufacturer: Graham
Brand: Epoch IV (or Verituf)
Density you use: 6250 (a lot) / 1600 (sometimes)
Tape length: 2400
Comments: 9 -- I'd give it a 10, but occasionally I have trouble
getting these puppies to auto-load, 'cause the leader sticks to the
rest of the reel or gets a little chewed up---this could be a function
of our tapedrives, tho'. I've never lost a bit from these tapes, and
I've been using about a dozen of them over over the last 6 years on
an occasional basis. They've survived a number of moves, lots of
different tapedrives, and other sorts of abuse. Yes, I would trust
my dissertation to one of these tapes.
Rich Kulawiec, rsk@j.cc.purdue.edu, j.cc.purdue.edu!rsk
From: seismo!gorgo.att.com!bsteve (on Monster Island)
CDC 1600 BPI 2400 FT - several cases, mean errors was 8 over 1 year.
Scotch 700 1600 BPI 2400 FT - several cases, mean errors was 2 over 1 year
Graham Magnetics 1600 BPI 2400 FT - several cases, mean errors was 3 over 1 yea
r
Graham Magnetics 1600 BPI 2400 FT - several cases, mean errors 15 over 3 years
DEC 1600 BPI 2400 FT - over several cases, mean errors was 9 over 1 year
DEC 1600 BPI 2400 FT - over several cases, mean errors was 23 over 3 years
Errors represent both CRC and parity errors recorded per tape, but do not
represent a complete write and read of the media. All of the data was taken
from backup error logs over a 3 year period. I am reluctant to rate them on
a 1 to 10 scale since the performance varies dramatically over several years.
The Graham Magnetics tapes varied from dramatically from lot to lot, while
the Digital tapes were consistantly mediocre. I should add that the Digital
tapes had by far the largest number of unrecoverable errors resulting in the
disposal of the tape.
Steve Blasingame (Oklahoma City)
From: harvard!eplunix!ijs (Ishmael J. Stefanov-Wagner)
Manufacturer: CDC
Brand: Alpha Phi
Density you use: 800 1600 6250
Tape length: 600 1200 2400
Comments: 9 Our standard workhorse tape
Manufacturer: 3M
Brand: Scotch 700
Density you use: 1600
Tape length: 1200 2400
Comments: 5 Gunks up guides and vacuum columns
Manufacturer: unknown
Brand: INMAC Standard
Density you use: 800
Tape length: 2400
Comments: 1 Useful solely for Write-Only/Read-Never files
|\___/| Ishmael J. Stefanov-Wagner
From: [another anonymous contributor - Ken]
Subject: Re: 3M Blackwatch Magtapes
Manufacturer: 3M
Brand: Blackwatch
Size: 2400'
Density: 6250
Usage (daily backup, weekly, etc): daily,weekly,monthly
Rating (out of 10): ?
Comments:
No problems so far. We have used them for almost a year. We have
needed to read them several times and have had no problems reading
recent tape. We have not had the need (and lets hope we never do) to
read old tapes.
From: [yet another anonymous contributor - Ken]
Manufacturer: BASF
Brand: Endura
Size: 2400' 10.5"
Density: 6250, 1600
Usage (daily backup, weekly, etc): backup, tar archives
Rating (out of 10): 3
Comments: maybe 1 in 30 bad out of the box. Wear out quickly,
to point where can't read 5 or 10 places on tape.
Sometimes read after write is OK, but can't read for a restore
a month later
Manufacturer: 3M
Brand: 777
Size: 2400
Density: 1600
Usage (daily backup, weekly, etc): backup, tar archives
Rating (out of 10): 2
Comments: wear out and go bad
Manufacturer: 3M
Brand: Black Watch
Size: 2400
Density: 1600
Usage (daily backup, weekly, etc): backup, tar archives
Rating (out of 10): 5
Comments: Pretty good, but occasionaly (1 in 30) bad out of the box.
Manufacturer: Graham Magnetics
Brand: Summit
Size: 2400
Density: 6250, 1600
Usage (daily backup, weekly, etc): tar archives
Rating (out of 10): 8
Comments: never any problem. Always work unless the tape drive
malfunctions.
Manufacturer: Graham Magnetics
Brand: Epoch 480
Size: 2400
Density: 6250, 1600
Usage (daily backup, weekly, etc): tar archives
Rating (out of 10): 9
Comments: never any problem. Always work unless the tape drive
malfunctions.
Manufacturer: Graham Magnetics
Brand: Ultimag
Size: 2400
Density: 6250, 1600
Usage (daily backup, weekly, etc): tar archives
Rating (out of 10): 10
Comments: never any problem. Always work unless the tape drive
malfunctions. I am told it has an impressive warranty: if tape
fails and you lose the data, will pay up to $5,000 data recovery
costs (re-keying, etc.). If true, this is impressive.