From: timhu@ico.isc.com (Timothy Hu)
Subject: QIC-150 tape drives
Organization: Interactive Systems Corp., Boulder CO
Date: Fri, 18 Dec 1992 20:45:40 GMT

Ray (toy@soho.crd.ge.com),

Okay, I see what you're aiming for in your system. That 300-600 Mbit/sec tape
drive that you mention is most likely a burst rate: The tape mechanism fills a
buffer full of data and when the high-water mark is reached, the controller spits
the data out over the bus at that rate. Vice versa as well. This would reduce bus
contention quite a bit.

If we look at the data density for QIC-150 tape drives, we can see what its
maximum physical transfer rate is:

10000 bpi * 90 ips = 900000 bits/sec (~ 100Kbytes/sec).

This agrees with advertised xfer rates of 6 to 7 Mbytes/min. Right now, I'm
installing a SCSI Archive Tape drive (the Viper 2150S unit) into my PC. I'm
looking into buying an Adaptec 1542 SCSI host adapter. Most mail order places
advertise this as the 1542BK, 1542KIT, 1542BKIT, or some such other nomenclature.
This is the host adapter itself along with some drivers to get it working under
DOS/UNIX/OS2/WINDOWS/etc. The most important piece of software for DOS is the ASPI
drivers. This piece of software is *really* important. You can call Adaptec's BBS
and get all the inside scoops on this (408-945-7727). Believe me, when you start
looking into SCSI/Adaptec, you'll need to capture the information from this BBS.
Adaptec has a wide range of hardware/software configurations to choose from and it
would behoove you to get the info.

I chose the QIC-150 format over the smaller CMS/Irwin variety (the kind that use
DC2000/DC2120 tapes) for several reasons:

1. QIC-150 type cartridges cost the same as, if not less than, the DC2000/DC2120s.
	--> $15 to $24 for 6150, $1-$5 more for 6250, DC2000/DC2120 range from
		$15 to $25.
2. QIC-150 data rates are a lot higher (I think).
3. QIC-150 drives and tapes have years and years of proven reliability.
	DC2000/CD2120 technology has been around for a few years.
4. With QIC-150, you get to use the same tape as those used with many SUNs, SGIs,
	etc. provided that you write the tapes in the same format (e.g. 386 UNIX).
5. QIC-150 type cartridges hold a **bunch** --> up to ~300 meg (compressed using
	6150 tapes and ~500 meg (compressed using 6250 tapes)!
6. QIC-150 drives seem to be built sturdier.

Bad things:

1. They cost a lot. QIC-150 drives (SCSI/QIC02/etc) cost $600-$900 new.
	However, used ones go for $150-$200. Getting a used tape drive is
	less risky than getting a used disk drive. A tape drive isn't in use all
	the time like a disk drive. I would think that a tape drive gets used
	around 3 hrs a week or so on the average. Even if it is used for backup
	every single day, it gets used maybe 1 hr a day. Not only that, the
	mechanisms in a tape drive aren't spinning at 3000+ RPM. The tape is
	running at 90 ips. The point is that getting a used QIC-150 tape unit isn't
	as risky as getting a used disk drive because the duty cycle is a *lot*
	smaller.
2. Requires an adapter (e.g. SCSI). Cost = ~$100 and up.

I can't think of any more Good/Bad things at the moment. I'll let you know as soon
as I think of them.

Recommendations:

I recommend a WANGTEK unit. I believe the model numbers are 5150ES and 5250ES. I
think that the 5150ES unit is the standard 150meg unit and the 5250ES is the
250meg unit that can store more than 1Gig with the 6525 tapes. Archive is also a
good choice. The prices of the two brands are similar ($600-$900) for the 150meg
units. The 250meg units are gonna be more -- how much more? I don't know. Why do
I recommend a WANGTEK unit? They're the largest manufacturer of QIC-150 type
drives and I've had prior experience with their 120meg unit on a PC. No bad
experiences.  I haven't had experience with their 150meg or 250meg units in a PC
but I don't believe that it's gonna be any different. However, I've had some
problems with the DC2000/DC2120 type tape drives. I gotten them solved and it runs
okay now, but I'd rather stay away from this relatively immature product. I'm not
saying that the DC2000/DC2120 type tape drives are bad. They're not. My father
uses one on his machine (getting him to use it is another problem) and it seems to
get the job done. For a new unit, you can't beat the price of a DC2XX0 unit. All
varieties of drives (QIC-150, DC2000, etc) might come with software (drivers, backup
utils, etc) depending on where you get it from. For some people, the QIC-150 is
not the right choice. For others (like me), it's the only choice.

Sorry to ramble on.

Any more questions/comments? Just let me know.

Cheers,
Tim
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