cslater@ibmpa.UUCP (Charlie Slater) (02/08/90)
In article <7527@lindy.Stanford.EDU> CN.RNA@forsythe.stanford.edu (Richard Anderson) writes: > >I have a question regarding the "dump" command. The AOS4.3 >System Administration manual (which I have found very useful >and clearly written) has a chapter on Backup & Restore, in which >a refererence is made to the 6157 streaming tape drive, followed >by an example of the dump command: > > dump 0suf 2600 /dev/st0 /dev/rhd0a > >They use a value of 2600 ft for the length of the tape and accept >the default density of 1600. However, the DC6150 tapes I use on my >6157-002 drive are 600 feet long and have a density(?) of 12,500 >ftpi. Tape drives are not my specialty but I will give this a try. A more practical measure of the density is 12K bytes / foot. The type 2 drives write at a higher density, but it will be easier for users of dump to pretend the type 2 drives make their tapes twice as long. The example's use of 2600 is not appropriate for the streaming device. Dump's default length for a streaming tape in the BSD Tahoe release is 1700 feet. This is 450 feet times 4 tracks (presumably appropriate for Tahoe hardware). In IBM 4.3, the default length is 4000 feet (450 x 9). For a 600-foot tape with a type 1 (original model) drive, use 5400 (or 5300 if you are as paranoid as I am). If you have a type 2 (double density drive), you can specify 10000. At 12K bytes per foot, you can get 60 megabytes on a 600 foot tape (120 megabytes using a type 2 drive). This posting is based on my personal experience and examination of the dump source code. It does not represent the official postion of IBM. Any errors are my own responsibility. -- charlie slater uunet!ibmsupt!cslater (UUCP) cslater%ibmsupt@uunet.uu.net (Internet) cslater@ibmpa.tcspa.ibm.com (IBM internal internet)
CN.RNA@forsythe.stanford.edu (Richard Anderson) (02/23/90)
In article <7527@lindy.Stanford.EDU> I asked a question about
the dump command of AOS4.3 when used with a 6157-002 tape drive.
Based on information from IBM and elsewhere, I have concluded
that I should use the following form of the dump command when using
type DC6150 tape:
dump 0usdf 10800 10000 /dev/st0 /dev/rhdxy
We are using an IBM 6157-002 Tape Drive, which requires either
of the following 3M Tape Cartridges:
DC600A 600 ft 12,500 ftpi 550 oersted QIC-120 15-track 125 MB
DC6150 600 ft 12,500 ftpi 550 oersted QIC-150 18-track 150 MB
(the latter used to be called DC600XTD)
The effective tape length is derived from the length of the tape
(600 ft) multiplied by the number of tracks (18 for DC6150 tape)
= 10800 ft.
According to a source at IBM:
"The density written to the tape is hardware controlled and can not
be changed. The 6157-001 writes at 10,000 ftpi (flux transactions
per inch) which is approximately equivalent to a density rating of
8,000 bits per inch. The 6157-002 writes at 12,500 ftpi which is
equivalent to a density rating of 10,000 bits per inch."
Thanks for the help of all who responded to me.
Richard Anderson
Stanford University Libraries
cn.rna@forsythe.stanford.edu