Thread View: comp.sys.next.sysadmin
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Started by Patrick Robinson
Mon, 06 Apr 1992 18:41
"dump" params for DAT
Author: Patrick Robinson
Date: Mon, 06 Apr 1992 18:41
Date: Mon, 06 Apr 1992 18:41
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intend to use dump/restore forever, I'd sure like to understand how to make
it work.
Here's the problem: I'm having trouble understanding the man page for the
dump command. Down under the notes for 'DUMPING TO EXABYTE TAPE', there's
an explanation about setting the s paramter, which specifies tape size in
feet. They make the claim that a 1.985 Gb Exabyte tape (120 minute 8mm)
would be equivalent to 1,332,183 feet of 1600 bpi reel-to-reel tape. I
don't see where they get that number. According to my calculations:
1.985 Gb 1,073,741,824 bytes 8 bits 1 in 1 ft ~
* ------------------- * ------ * ---------- * ----- = 888,074 ft
1 Gb 1 byte 1,600 bits 12 in
rather than 1,332,183 ft.
Where am I going wrong? Where has my logic gone haywire?
The bottom-line question is: how do I set dump density and size (in feet)
for a 90m DAT tape? Oh... this drive does DCLZ compression.
Thanks,
-Patrick Robinson
Extension Information Systems
Virginia Tech
pgr@ramandu.ext.vt.edu
Re: "dump" params for DAT
Author: Patrick Robinson
Date: Mon, 06 Apr 1992 19:42
Date: Mon, 06 Apr 1992 19:42
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I wrote: > intend to use dump/restore forever, I'd sure like to understand how to make > it work. Strange. This originally said "Although I don't intend..." -Patrick pgr@ramandu.ext.vt.edu
Re: "dump" params for DAT
Author: Scott Turner
Date: Tue, 07 Apr 1992 07:43
Date: Tue, 07 Apr 1992 07:43
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In article <3699@vtserf.cc.vt.edu> pgr@ramandu.ext.vt.edu (Patrick Robinson) writes: |> intend to use dump/restore forever, I'd sure like to understand how to make |> it work. |> |> Here's the problem: I'm having trouble understanding the man page for the |> dump command. Here's what I use on 60m tape: dump 0usdf 2352 593480 /dev/rst0 Divide 2352 by 12 and you get roughly 60m. The 's' param seems to be in inches, not feet. Dump/restore don't grok DCLZ compression. Unless you have some readout on your drive it will basically just boost your throughput. You will also find the file recovery speed of restore to be somewhat ridiculous, it doesn't block address the tape, it streams it. Scotty
Re: "dump" params for DAT
Author: Sherwood Botsford
Date: Tue, 07 Apr 1992 20:03
Date: Tue, 07 Apr 1992 20:03
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Patrick Robinson writes > intend to use dump/restore forever, I'd sure like to understand how to make > it work. > > Here's the problem: I'm having trouble understanding the man page for the > dump command. Down under the notes for 'DUMPING TO EXABYTE TAPE', there's > an explanation about setting the s paramter, which specifies tape size in > feet. They make the claim that a 1.985 Gb Exabyte tape (120 minute 8mm) > would be equivalent to 1,332,183 feet of 1600 bpi reel-to-reel tape. I > don't see where they get that number. According to my calculations: > > 1.985 Gb 1,073,741,824 bytes 8 bits 1 in 1 ft ~ > * ------------------- * ------ * ---------- * ----- = 888,074 ft > 1 Gb 1 byte 1,600 bits 12 in > > rather than 1,332,183 ft. Two things: 1. The man page is wrong. A single tape with the stated capacity is actually about 110,000 feet. 2. 1600 bpi is for *each* track of the 9 track tape. Normally one track was for parity, so it worked out to 1600 bytes/inch of tape. This confusion above makes your answer correct. (eliminate the 8bits/byte conviersion) The only reason you care at all about this is that dump multiplies it's default bpi x 12 x length in feet to get the amount of stuff that will fit on the tape. This is used to figure out when to ask the operator to change tapes. So you could do this by either telling dump that your tape is only 30 meters long, and it's density is a zillion bits per inch, or by letting it assume a 9 track tape, that's rather long.
"dump" params for Archive tape?
Author: Steve Anderson
Date: Wed, 08 Apr 1992 12:20
Date: Wed, 08 Apr 1992 12:20
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Who's got a good set of parameters to feed dump for dumping to 150Mb Archive (viper) tapes? I really hope the scsi tape support in 3.0 is a bit more serious than it has been so far. --Steve Anderson
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