compress or native

[Vic S. Kelan]

Hi

Can I get ignite to compress the backup or is the only way it works in the native capacity mode for the tape?

Thanks

[RAC_1]

I do not think ignite does any kind of compressing. the capacity of tape would matter.

[Stephen Keane]

Does the tape drive have a hardware compression facility? Usually the device file has something like "BEST" in the name.

[Eric Antunes]

Hi Vic,

Execute de following to see yout tape devices:

#ioscan -fnCtape

It usually use /dev/rmt/0mn for make_tape_recovery.

Ignite uses "tar" so the backup archive will be compressed.

Best Regards,

Eric Antunes

[Eric Antunes]

Instead of

"It usually use /dev/rmt/0mn for make_tape_recovery."

I wanted to say:

I usually use /dev/rmt/0mn for make_tape_recovery.

[Vic S. Kelan]

Hi All,
thanks for the response, yes the device has BEST, so it supports HW compression I guess.
tape 0 0/1/1/1.2.0 stape CLAIMED DEVICE HP C7438A
/dev/rmt/0m /dev/rmt/c3t2d0BESTn
/dev/rmt/0mb /dev/rmt/c3t2d0BESTnb
/dev/rmt/0mn /dev/rmt/c3t2d0DDS
/dev/rmt/0mnb /dev/rmt/c3t2d0DDSb
/dev/rmt/c3t2d0BEST /dev/rmt/c3t2d0DDSn
/dev/rmt/c3t2d0BESTb /dev/rmt/c3t2d0DDSnb

if i specify /dev/rmt/0mb for ignite by how much will it compress? 2:1?
Thanks

[Bill Hassell]

Compression, whether software or hardware, is *always& dependent on the data you are saving. Truly random data cannot be significantly compressed but a large database file with no records can be compressed 10:1. Unfortunately, the tape manufacturers have adopted 2:1 as a "typical" number but you cannot depend on this value. The only amount you can depend on is 1:1. Ignite is simply running pax (a tar/cpio program) so the tape drive will do what it can. NOTE: current versions of Ignite/UX will handle multiple tapes, but since most vg00 backups will fit on a single tape, this is usually not an issue. NOTE: Ignite/UX is designed as a root/boot disk restoration prgram, not a general purpose backup for all data.