backup with compressed cpio files ?

[Griff Smith]

In article <64 at estinc.UUCP>, fnf at estinc.UUCP (Fred Fish) writes:
> In article <9667 at smoke.BRL.MIL> gwyn at brl.arpa (Doug Gwyn (VLD/VMB) <gwyn>) writes:
> >	find . -depth -print | cpio -oc | compress | dd bs=5k > /dev/rmt0
> In order to ensure that dd writes 5K records I believe you have to
> specify "ibs" and "obs" to be different sizes, to force an internal
> buffer copy.

Only true if you are using the dd in V9.  It is only necessary that
you use ibs and obs rather than bs; the sizes can be identical.

> Substitute "ibs=1k obs=5k" for "bs=5K".

Why?  Unless you are working on a brain-damaged tape drive that can't
write blocks larger than 5k, why not use large blocks to get more on
the tape.  20K, maybe.  You're going to read the tape with dd anyway,
and cpio won't have trouble reading the pipeline from compress.
Try "ibs=8k obs=20k".

> Also note that the last buffer may not be a full 5k, which may confuse
> a cpio that reads the tape directly.

Cpio can't read the tape directly, it's compressed.

> With compress, one read error and you're SOL as far as recovering the rest
> of the data.

Which is a good reason to forget the whole suggestion anyway.
> -- 
> # Fred Fish, 1835 E. Belmont Drive, Tempe, AZ 85284,  USA
> # 1-602-491-0048           asuvax!{nud,mcdphx}!estinc!fnf
-- 
Griff Smith	AT&T (Bell Laboratories), Murray Hill
Phone:		1-201-582-7736
UUCP:		{most AT&T sites}!ulysses!ggs
Internet:	ggs at ulysses.att.com