backup to 150-MB cartridge tape

[Don Lewis]

In article <8624 at brazos.Rice.edu> cerveza!gary at sunkist.west.sun.com (Gary Cattelino) writes:
>> This is in reponse to Danielle's question about backing up to 150-MB tapes
>> instead of the 60-MB ones.  These are the parameters I was told to use by
>> our Sun FE:
>
>> /usr/etc/dump [0-9]uctsdf 18 620 1250 /dev/nrst0 /dev/rsd6[a-h]
>
>On page 74 of the Sparcstation 1 Sun System and Network Manager's Guide
>(the little books you get when you buy a Sparc 1) it says to use:
>
>/usr/etc/dump 0cusdtf 590 1200 18 /dev/nrst0 filesystem
>
>In the discussion they say to use 590 to handle media errors (600 feet
>minus 10 feet to handle media flaws).  Well, I just looked at a DC6150 and
>it says 620 feet.  Maybe the proper size to use for these tapes is 610
>feet?  It also says the density is 1200, not 1250 from the previous
>posting.  Which is correct?  I've been using 1200 with no problems.  Maybe
>a density of 1250 will allow me to store more on one tape?
>
>Anyone know the answers to these questions?

Disclaimer, I don't have any authoritative info.  A couple of weeks ago I
did some capacity calculations and figured that if the density is 1250,
then the capacity works out about right.  Also, I just noticed that the
default density with the "c" option is 1000 and DC300XL/P tapes are rated
at 10000 ftpi, and that DC6150 tapes are rated at 12500 ftpi.  It sounds
like the density should be 1250.

I have the following tapes in front of me:

	3M DC6150					600 feet (182.9m)
	Carlisle DC600XTD (Series II Gold Plus)		620 feet (189.0m)
		DC600XTD is supposed to be the same as DC6150
	DEI Series II Gold (appears to be DC600A)	600 feet (182.9m)
	3M DC600A					600 feet (182.9m)
	3M DC600A					620 feet (189.0m)

So much for standardization.

It looks to me like the proper parameters are:
	length 590/610 (depending on the tape)
	density 1250

By the way.  There is supposed to be a QIC-120 tape format which holds 125
Meg on a tape.  The difference comes from putting only 15 tracks on the
tape instead of 18.  I tried writing some DC600A tapes on one of the
Wangtek drives here and it seems to hit EOT at around 130 Meg, as opposed
to 155 for a DC6150.  According to the labels on the tapes, the lengths,
magnetic properties, and rated density are the same.  Apparently the drive
can sense the tape type and do the appropriate thing.  I have not yet
tried this on an official Sun (Archive?) drive.  Has anyone heard if this
is actually supposed to work?  

Don "Truck" Lewis
Internet:  del at mlb.semi.harris.com