Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!tut.cis.ohio-state.edu!uc!shamash!zeke From: zeke@shamash.cdc.com (Robert Scott) Newsgroups: comp.unix.admin Subject: Re: Dumping to an exabyte tape drive Summary: Numbers used only by DUMP, not by device driver. Keywords: Exabyte dump args Message-ID: <25394@shamash.cdc.com> Date: 4 Sep 90 19:01:21 GMT References: <1990Aug29.143657.20588@siesoft.co.uk> <877@iiasa.UUCP> Organization: Control Data Corporation, Arden Hills, MN. Lines: 69 In article <877@iiasa.UUCP>, wnp@iiasa.AT (wolf paul) writes: > In article <1990Sep1.143812@suned1.nswses.navy.mil> jht@suned1.nswses.navy.mil (Jim Tibbs) writes: > > Stuff deleted. > > These figures seem quite inconsisten. Which is correct? > Would someone at SUN care to comment, ideally the person who wrote > their drivers? > > A Standard Tape has a density of 6250 bpi and a length of 2300 feet > > Jim Tibbs specifies a density of 43000 bpi and a length of 12000 feet > > Derick Linegar specifies 4100000 bpi and a length of 5190 feet > > Frank Bresz specifies density of 54000 bpi and a length of 6000 feet > > -- These numbers are really only used by the DUMP program to determine length of tape for volume and "time to finish" estimates. The actual device driver will correctly write to the device regardless of what you specify in DUMP, but the dump parameters affect how much of the tape you actually use. We are using a Delta Microsystems driver here on Sun OS 4.01. I quote from the Delta Microsystems SS-2000T User's Guide (attributed, but not used by permission): Using dump with a 2000T drive is essentially the same as using dump with any other tape device, except that you get a lot more information on each tape. Because of the difference in bit density between the 2000T and a normal 9-track drive, and because dump uses the 9-track drive as its reference in calculating the tape length, the tape length you provide for the 2000T must be the effective tape length (as if it were a 1600 bpi 9-track tape capable of storing the same number of megabytes as the 2000T tape). Formula for computing the tape length parameter: size = (((512*blocking factor)+1920)/blocking factor) * ((total Kbytes on tape - 2048)/10667) The blocking factor is how many 512 byte buffers (the standard buffer size for dump) should be used in 1 tape record (which by default is 1024 bytes for Delta). So BF is 2,4,6... (default of 2). Optimum for Delta is BF=124, or 62 Kbytes/block. Total kbytes per tape is straight from a table as follows (for Sony P6 tapes, for domestic U.S.): 15 minute tape: 258 Meg 30 minute tape: 516 Meg 60 minute tape: 1032 Meg etc.... Example for a full dump command to a Sony P6-120 tape using optimal block size: dump 0fbs /dev/device_name 124 103400 partition_name Hope this helps. Zeke -- ~~~~~~~~~~~ From the Shrine of the "Last Gasp of ETA Systems" ~~~~~~~~~~~~~ Extra zesty disclaimer: MINE! MINE! ALL MINE! Robert K. "Zeke" Scott internet: zeke@eta.cdc.com Control Data Corp, Supercomputer Support Group