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Top Forums UNIX for Advanced & Expert Users can anyone help Post 5894 by Kelam_Magnus on Saturday 25th of August 2001 03:33:55 PM
Old 08-25-2001
Lightbulb

EricB,

You probably know this, but I will mention it anyway.

When you compress, in most cases, you get around 80% compression. While this will save space on your tapes, it will also slow down recovery from the tape should that be necessary.

If this is data that is being archived for long term storage, then your need to compress would be a valid one.

Just remember, the more you do to the data to get it onto the tape, the longer it will take you to get it off of the tape later.

Also, you may want to look at "gzip" as well. It may get better compression than "compress", if I remember correctly.

 
TCOPY(1)						    BSD General Commands Manual 						  TCOPY(1)

NAME
tcopy -- copy and/or verify mag tapes SYNOPSIS
tcopy [-cvx] [-s maxblk] [src [dest]] DESCRIPTION
The tcopy utility is designed to copy magnetic tapes. The only assumption made about the tape layout is that there are two sequential EOF marks at the end. By default, the tcopy utility will print information about the sizes of records and files found on the /dev/sa0 tape, or on the tape specified by the src argument. If a destination tape is also specified by the dest argument, a copy of the source tape will be made. The blocking on the destination tape will be identical to that used on the source tape. Copying a tape will yield the same program output as if just printing the sizes. The following options are available: -c Copy src to dest and then verify that the two tapes are identical. -s maxblk Specify a maximum block size, maxblk. -v Given the two tapes src and dest, verify that they are identical. -x Output all informational messages to the standard error instead of the standard output. This option is useful when dest is given as /dev/stdout. SEE ALSO
mt(1), mtio(4) HISTORY
The tcopy command appeared in 4.3BSD. BUGS
Writing an image of a tape to a file does not preserve much more than the raw data. Block size(s) and tape EOF marks are lost which would otherwise be preserved in a tape-to-tape copy. End of data (EOD) is determined by two sequential EOF marks with no data between them. There used to be old systems which typically wrote three EOF's between tape files. The tcopy utility will erroneously stop copying early in this case. When using the copy/verify option -c, tcopy does not rewind the tapes prior to start. A rewind is performed after writing, prior to the ver- ification stage. If one does not start at the beginning-of-tape (BOT) then the comparison may not be of the intended data. BSD
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