Thanks everybody for your helpful responses. All of them had
different and useful tips. I'll try to summarize and add some
comments.
i) Regarding compression on FreeBSD: thanks John (Merryweath) for
reminding me of mt.
I have now turned HW compression ON && host control ON and I can
manage it myself!
ii) Thanks Joshua & John (Jackson) for the tips on the tapelength when
using hardware compression. I'll try to lie to amanda :( for a few runs
and see what I get for every fs.
iii) After thinking a bit on what Gene wrote regarding hardware compression
("Generally speaking, the hardware compression should be disabled.") I
can only say that I haven't made a final decision and I'm just doing
my experience on this.
I thought about leaving the task to the tape drive, mostly
because both the client and the server (the only two machines we have)
are sometimes running important processes that need CPU resources
badly. And even when they're not, the times are not predictable
(sometimes we leave things running overnight, for a whole weekend, or
even for weeks ...)
iv) Regarding what Gene wrote about drives switching compression
back on (if they find a compressed tape): AFAIK the HP DAT 40 will
read compressed tapes no matter what the compression setting is. (Even
if you set the jumpers on the hardware to turn both compression and
host control to OFF). But I cannot tell if this means that compression
will get turned ON for writes afterward (I haven't actually
tested it).
And finally
v) Gene said: "Any partition thats that much gzipped already, should have the
compression turned off, doing a straight tar of it."
Again, I'm a newbie, and if I decided not to use tar, was not based on
my own experience but from what I've read elsewhere.
I'd like to know your points here. I have avoided tar, because earlier
on when I did backups manually (i.e. without amanda) I had a few
problems with tar (FreeBSD tar, v1.11.2), and upon
reading several mail archives with the same or similar problems
(quitting after too many errors, even when tar started
extracting/reading OK) other people suggested avoiding tar in favor of
dump.
But again, I'm open to be converted back to tar if I can trust it.
(I know that while installing amanda's freebsd port, it required
gtar-1.13.25 so perhaps I should give now gtar a chance?)
Thanks again everybody,
Fernan
