SUMMARY: dumping to a 5Gb 4mm dat tape

From: Andrew George (
Date: Thu Jun 09 1994 - 17:27:39 CDT

Dear Sun Mangers

Thankyou all For your responses Re Dumping to 4mm Dat drive using Solaris 1.1.1.
It seems that a few of you have found the same problem.

Here is what I originally posted:

----- Begin Included Message -----
Hi Sun-managers,

When dumping to a Sun 4mm Dat drive, using Solaris 1.1.1, I can only backup
aprox 2.5GB of data using rst0 and about 3.5GB of data using rst8.
The tape is 90m long. Should I be using a tape length of 120m?

Can anybody tell me what the correct parameters are for Dump using a 4mm Dat
drive under Solaris 1.1.1?

Answerbook for Solaris 2.3 says to use a blocking factor of 96 whereas
a document in sunsolve says to use 126.
Which is right? Any other hints or tips?

Thanks in advance....


----- End Included Message -----

The concensus seems to be if you want to get anything close to 5Gb on a dat
tape, then the device must be /dev/rst8 or higher. eg, rst16, rst32.

120m tapes are only for the newer DDS-II tape drives.

So far I've used the parameters from Chris Wozniak below and am getting alot
closer to the 5Gb SUN advertise.

Chris Wozniak TISC <>

b-factor of 126 is OK, or you may use c (cartridge) switch with the
same effect.
s = size = 5000 ficticious tape length
d = density = 61,000 real tape density.
Send to rst8, rst16 or rst32.
I've tested it with above parameters and got 4.9 GB onto tape,
close enough to the spec.

Many thanks to Chris and the following Sun Managers who also replied with
slightly different parameters and suggestions :- (David N. Edwards)
Here's what I use (Sparc-2 with Sun's DAT drive,
Running Solaris 1.1.1_U1 not rev. B, 90M tape):

        /usr/etc/dump 0ubsdf 96 7142 61000 /dev/nrst0 ${FILESYS}

The lenths people suggested from the net were: 10240 for 90M tapes, and
                                                6656 for 60M tapes.

Martin Kalugin <>
I use the follwing parameters:-

dump 0udsbf 61000 10240 96 /dev/nrst8 /dev/sd0g

these are the options I use, and they seem to be working fine :

                0dsbfu 54000 6000 96

Dave Mitchell <>

Sun's "5Gb" drive is a 2Gb drive + compression. Getting 3.5Gb in
compressed mode is reasonable, 5Gb is unrealistic. Complain to your
nearest Sun salesman about marketing hype....

>The tape is 90m long. Should I be using a tape length of 120m?

No. 120M tapes are only suitable for certain types of drive (DDS-2)
which I dont believe Sun's drive is.

>Answerbook for Solaris 2.3 says to use a blocking factor of 96 whereas
>a document in sunsolve says to use 126.

shouldnt make that much difference - I'd recommend 126.

This archive was generated by hypermail 2.1.2 : Fri Sep 28 2001 - 23:09:03 CDT