Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!samsung!munnari.oz.au!cluster!metro!news From: gopher@extro.ucc.su.oz.au (John McQueen) Newsgroups: comp.sys.mips Subject: Re: QIC-120 tapes with dump (was Re: /proc and other questions) Message-ID: <1990Feb5.235525.18017@metro.ucc.su.oz.au> Date: 5 Feb 90 23:55:25 GMT References: <35264@mips.mips.COM> <1529@uakari.primate.wisc.edu> Reply-To: gopher@extro.ucc.su.oz.au (John McQueen) Organization: University Computing Service, Uni. of Sydney, Australia. Lines: 114 In article <1529@uakari.primate.wisc.edu> bin@primate.wisc.edu writes: >|>>In article <1644@skye.ed.ac.uk> richard@aiai.UUCP (Richard Tobin) writes: >|>>>(2) Can someone tell me the right length/density parameters for using >|>>>QIC-120 tapes with dump? > >|>In article <35223@mips.mips.COM> rogerk@mips.COM (Roger B.A. Klorese) writes: >|>>We use (real size * ~95%) for size, so ~570 feet, and 16000 for density. > >| In article <1990Jan31.011355.14288@metro.ucc.su.oz.au> gopher@extro.ucc.su.oz.au (John McQueen) writes: >|>I just checked our script - we use length=600 and denisity=30000. >|>Our dumps work fine - why the big difference in density?? > >From article <35264@mips.mips.COM>, by rogerk@mips.COM (Roger B.A. Klorese): >| Well, we may well be underusing our tapes. Let me do some testing... > >To John: I've found that that the dump program will sense the end of the >tape and ask you to switch properly, but will not correctly estimate the >amount of tape it's going to use, if the parameters are off. Question: do >you find on large filesystems that the number of tapes that dump estimates >that it will use it accurate? We have operators that do our dumps, so I'm not sure. I just set ours up so that it works. > >I've found that 570/25000 will produce estimates that are slightly too low. >E.g., dump estimates that it will use .98 tapes, and actually uses slightly >more than 1 tape (it *does* sense end of tape and request the next). > I noticed on 6250 tape that dump gave me an estimate of .9? tapes and went over 1.? in the end. Another thing is the estimated time to completion seems to go up every time you change a tape. >So I would say that 600/30000 is too high, 570/25000 is a bit too high, >570/16000 is too low. Let's hear from others. Good tests are file systems >big enough to end up using just a bit more than one tape. Ok the question is how much data can you fit on a QIC-120 tape? I was informed that the amount of data is about 150MB. So a quick calculation reveals that at 600 ft the density is about 21000. At 570 ft the density is about 23000. So your figures seem right to me. Another question for people, is what are the correct s and d values for exabyte's? (we just got one last Friday). (Not that it matters too much you can fit about 4 filesystems to a tape anyway!!) John McQueen From: gopher@extro.ucc.su.oz.au (John McQueen) Newsgroups: comp.sys.mips Subject: Re: QIC-120 tapes with dump (was Re: /proc and other questions) Summary: Expires: References: <35264@mips.mips.COM> <1529@uakari.primate.wisc.edu> Sender: Reply-To: gopher@extro.ucc.su.oz.au (John McQueen) Followup-To: Distribution: Organization: University Computing Service, Uni. of Sydney, Australia. Keywords: In article <1529@uakari.primate.wisc.edu> bin@primate.wisc.edu writes: >|>>In article <1644@skye.ed.ac.uk> richard@aiai.UUCP (Richard Tobin) writes: >|>>>(2) Can someone tell me the right length/density parameters for using >|>>>QIC-120 tapes with dump? > >|>In article <35223@mips.mips.COM> rogerk@mips.COM (Roger B.A. Klorese) writes: >|>>We use (real size * ~95%) for size, so ~570 feet, and 16000 for density. > >| In article <1990Jan31.011355.14288@metro.ucc.su.oz.au> gopher@extro.ucc.su.oz.au (John McQueen) writes: >|>I just checked our script - we use length=600 and denisity=30000. >|>Our dumps work fine - why the big difference in density?? > >From article <35264@mips.mips.COM>, by rogerk@mips.COM (Roger B.A. Klorese): >| Well, we may well be underusing our tapes. Let me do some testing... > >To John: I've found that that the dump program will sense the end of the >tape and ask you to switch properly, but will not correctly estimate the >amount of tape it's going to use, if the parameters are off. Question: do >you find on large filesystems that the number of tapes that dump estimates >that it will use it accurate? We have operators that do our dumps, so I'm not sure. I just set ours up so that it works. > >I've found that 570/25000 will produce estimates that are slightly too low. >E.g., dump estimates that it will use .98 tapes, and actually uses slightly >more than 1 tape (it *does* sense end of tape and request the next). > I noticed on 6250 tape that dump gave me an estimate of .9? tapes and went over 1.? in the end. Another thing is the estimated time to completion seems to go up every time you change a tape. >So I would say that 600/30000 is too high, 570/25000 is a bit too high, >570/16000 is too low. Let's hear from others. Good tests are file systems >big enough to end up using just a bit more than one tape. Ok the question is how much data can you fit on a QIC-120 tape? I was informed that the amount of data is about 150MB. So a quick calculation reveals that at 600 ft the density is about 21000. At 570 ft the density is about 23000. So your figures seem right to me. Another question for people, is what are the correct s and d values for exabyte's? (we just got one last Friday). (Not that it matters too much you can fit about 4 filesystems to a tape anyway!!) John McQueen -- ________________________________________________________________________ John Scott McQueen | gopher@extro.ucc.su.oz.au University Computing Service, H08 | Phone: +61 2 6923495 University of Sydney, NSW 2006, Australia | FAX: +61 2 6606557