Tape Backup

[Chip Rosenthal]

In article <31 at abode.UUCP> eric at abode.wciu.edu (Eric C. Bennett) writes:
>I am looking for an internal drive (with a controller because I use an IDE
>controller on my HD. I want to save the other HD controller for a future
>drive anyway).

You are confused.  There are tape drives which connect to the floppy
disk controller (QIC40), but not hard disk controllers.  Even still,
you are correct not to want one.  They are ridiculous, flimsy, pokey,
kludgy little toys.

>I would be backup up a 200 MB hard drive. Any recommendations on what works
>best with XENIX and how big of a backup drive I should get?

Surprisingly, this is a fairly easy question to answer, because the choices
are limited.  At least they are if you rule out the crap `floppy tape'
drives.  There are three things you need to answer:

    - What interface technology?
    - What size?
    - Which manufacturer?

There are three different kinds of interfaces:  SCSI, QIC36, and
QIC02.  A SCSI tape drive will run off the same controller as other
SCSI peripherals, e.g. disks.  The other two types of tape drives
require a dedicated controller.  QIC36 controllers tend to be long-card
format (and a bit smarter) and QIC02 controllers tend to be short-card
format (and a bit stupider).  I strongly recommend SCSI as the first
choice.  However, if you've already got something other than SCSI
disks, then it's probably not justified.  (Especially if you are
running the AT version of XENIX!)  If SCSI is not appropriate,
then QIC36 is the way to go.

Next question is, `what size?'  The obvious answer is your tape needs
to be as big as the space you will be backing up.  The obvious answer
is wrong.  If you are the least bit intelligent about your backups -
in particular you do some form of incremental backups - you'd be
surprised at how small your tape really needs to be.  For example,
chinacat has 320MB of disk, and its backup is a 60MB tape.  Once a
quarter, when I do a full backup it does indeed take a bunch of tapes.
However, all my daily and weekly incremental backups fit onto one
tape.  My backup policy is very conservative, but it still takes me
only one tape to hold an incremental.  And I only need to rummage
through (at most) three backup sets to locate any file.

With that said, I think 60MB is too small for 320MB - the 60MB tape
was added when chinacat only had 150MB of disk.  I think a good rule
of thumb is your tape drive needs to be at least 1/3 the size of the
disk.  Since you've got a 200MB disk, you need a 66.7MB tape :-)
Actually, I think 60MB would be fine for a 200MB disk, but if you
were to add any more, 150MB might be preferable.

The final question is which vendor?  That's the easiest of all because
there are only two:  Maynard and Wangtek.  Maynard drives used to be
called Archive.  Everything else, from Everex to Tecmar to Mountain is a
Wangtek drive in somebody else's box.  I've heard very good things about
the Maynard drive (in particular the VP60/VP150 Viper series), but have
not first-hand experience with them.  I've been through many Wangtek
drives, all with good results.  I think either manufacturer, under whatever
name you find, will be satisfactory, and the key factor is going to be
price.

One last point - there are two drawbacks to a 150MB tape over 60MB.  First
is obviously price.  The second is that the QIC24 recording format is
readable but not writable by 150MB tape drives.  You can make a 60MB tape
on a 150MB drive, but do not assume it can be read back on a 60MB drive.
You will get badly burned by that assumption.
-- 
Chip Rosenthal  512-482-8260  |  If software look-and-feel can be protected,
Unicom Systems Development    |  then I'd like to claim a copyright upon
<chip at chinacat.Unicom.COM>    |  `Memory fault - core dumped'.