topic Re: DDS3 Compressed? in Operating System - HP-UX

DDS3 Compressed?

Dave La Mar — Thu, 27 Dec 2001 18:06:59 GMT

I ran fbackup -0i path/to/file -f /dev/rmt/1mn
for a DDS 3 tape.
The file is 22g.
I was not asked for addtional tapes.
Does this mean it compressed automatically?
DDS 3 is 24g compressed.
How do I know the entire file was backed up?
Thanks for any input.
dl

Re: DDS3 Compressed?

harry d brown jr — Thu, 27 Dec 2001 18:24:01 GMT

Dave,

you can use frecover, with the "-N" option to list the files on the tape (which will list the "size", which should match what you backed up.

live free or die
harry

Re: DDS3 Compressed?

Dave La Mar — Thu, 27 Dec 2001 18:31:13 GMT

Excellent Harry, Just what I was looking for.
Will try this.
Thanks.
dl

Re: DDS3 Compressed?

Mark Greene_1 — Thu, 27 Dec 2001 18:33:58 GMT

You can also run the fbackup with the -v option to see more messages during the process. Using a log file to which to route both standard out and standard error while using this flag is advisable, as there may be several screens' worth of text, depending upon how many files are being backed-up.

--
mark

Re: DDS3 Compressed?

Bill Hassell — Thu, 27 Dec 2001 19:07:58 GMT

It's important to note that the 'compressed' capacity is nothing but a marketing term and should not be used to determine whether you have enough tapes to backup your system. The capacity of DDS3 is 12 GB. Anything more is 100% dependent on the actual data.

Highly compressable data contains long patterns of the same information or repeated combinations of short data strings. SO if you create a large test file using the prealloc command, that file will be very compressable, perhaps 100:1 or more. But since prealloc only creates a file full of zeros, the result isn't very useful.

If you use the lssf command on the device file, you should see that the BEST density will be selected, meaning compression is turned on. If the file won't completely fit on the tape, fbackup will stop and ask for a new tape.

To see the actual compression ratio on a tape, get a copy of the tapeinfo program from: ftp://contrib:9unsupp8@hprc.external.hp.com/sysadmin/programs/tapeinfo/

Re: DDS3 Compressed?

Dave La Mar — Thu, 27 Dec 2001 19:17:04 GMT

Bill -
You are correct. I shows best density.
Thanks.
dl

Re: DDS3 Compressed?

Dave La Mar — Thu, 27 Dec 2001 20:38:50 GMT

For those reading this thread-
The below listed the files only and not sizes.

frecover -f /dev/rmt/1m -rNv > /tmp/logfile 2>&1

The below listed the index which includes the files and sizes.

frecover -I /tmp/logfile2 -f /dev/rmt/1

Thanks people.
dl