[mod.computers.vax] Wanted: VAX/VMS-software to test tapes.

DEGROOT@HWALHW50.BITNET (Kees de Groot, tel.3557 [DEGROOT@HWALHW50]) (01/20/87)

Wanted: Software for VAX/VMS to test tapes.

         We are looking for software to test tapes.

         The software should write on the tape and read back
         afterwards in order to find bad spots. It should produce an
         indication of the quality of the tape.

         Of course, we could do a backup of the system disk to tape
         and after that copy the whole tape to the NUL-device looking
         for error-messages.

         But is there a more elegant way to do this?


        .KeesdeGroot   (DEGROOT@HWALHW50.BITNET)  o\/o  THERE AINT NO
        Wageningen Agricultural University         []   SUCH THING AS
        Computing Centre, the Netherlands         .==.  A FREE LUNCH!

carl@CITHEX.CALTECH.EDU.UUCP (01/21/87)

It sounds like you're not so much interested in testing the tapes as making
sure that whatever you've written to them can be read some time in the future.
If that's the case, and if, as your example seems to imply, the purpose of the
tapes will be as backups to your system's disks, then I can highly recommend
the software I've been using for several years now for just such purposes:
its most interesting features from your point of view are probably:
	1)  As it writes a tape, it checks to make sure that what it tried
	    to write is what was actually written.  If the read-compare fails,
	    the product tries rewriting that block of the tape several times;
	    if the problem persists, it adds information to the next block of
	    the tape indicating that the preceding block had problems, and
	    writes the data in question onto the tape elsewhere.
	2)  If that's not sufficient, the utility will, at the end of each tape
	    volume, rewind the tape, and verify that what is on the disk is
	    what's on the tape.
	3)  The program has a fair amount of redundancy in the format in which
	    it stores the data on tape, including (optional) group check blocks
	    which are the bitwise XORS of all the normal data blocks in a given
	    group (the number of blocks in a group is selectable by the user),
	    and (also optional) cyclic redundancy checks.
	4)  On multi-volume tape savesets, you need only mount the volumes
	    containing the data you want to restore, when you want to retrieve
	    the data from the tapes: there is no need to start at the beginning
	    of the save set and skip through until you get to what you want.
	5)  When any tape errors (either on read or on write) are detected, the
	    utility reports them, generally with an indication as to which of
	    the files you are dealing with might have been affected.
	6)  I have yet to have this product fail to restore a saveset it wrote.
	    In fact, there have been times when this utility was the ONLY
	    piece of canned software available that was able to read the media:
	    all other utilities gave up due to parity errors, invalid record
	    structures, and so forth:  yet this piece of software not only
	    read the tape without complaining too loudly, it restored the
	    entire saveset flawlessly.

The utility to which I refer, of course, is BACKUP, a part of every VMS system.