RE: [BackupPC-users] A question about tapes

[Brown, W. (M. ASL) <Mat...@me...>]

Hello all.

The easiest way I found to make an archive of any client directory was
to use the BackupPC_tarCreate command and direct it's stream to the tape
device.  I use the term "backup" when the client is sending data to the
backup server and the term "archive" when sending client data to a tape
device.

First, I created a copy of the perl script "BackupPC_tarCreate".  I
called it "tarCreate".  I have a DLT library (with a DLT8000 drive)
hanging off my backup server so I tweaked the tarCreate code: Line 129,
BufSize = 8388608 and Line 131, WriteBufSz = 8192.  For those of you
that care, in Linux, getting a DLT to stream can be an interesting
experience.  Using the mods above with a st buffer_kbs setting of 8192,
my DLT drive screams.  The archive still works without making the mods
but the defaults (20 * header) are way to low.  You should time your
writes before (default) and after making any mods.

To write to tape, you should also allow "others" to write to the tape
device.  On Solaris, they are in the /dev/rmt directory.  On my linux
box, I'm using /dev/nst0.

Then call tarCreate:
	tarCreate -h host -n dumpNum -s shareName files/directories >
/dev/nst0

I'm backing up "/usr/local" on host "wadetest".  I can send the entire
share to tape with the following command:
	tarCreate -h wadetest -n 0 -s /usr/local / > /dev/nst0

The client directory should be stable when you archive.  An archive can
take place while the client is being backed up but after it finished the
backup, there would be a chance the dump is removed (while you are
trying to archive).  I don't know the exact timing, tho, but it's best
if you don't do both at the same time.  For now, I either shutdown the
daemon or verify the dump won't go away.  It would be nice if one could
send a "lock <host>" with BackupPC_serverMesg.  Assuming the response
was "ok" and not "host busy" (with a backup), you could archive with no
worries.  Then, after you are done, send a "unlock <host>".  I'll add
that code as soon as I learn Perl.  :)  

Have phun!

- Wade




-----Original Message-----
From: Brown, Wade (MED, ASL) 
Sent: Tuesday, June 24, 2003 8:40 AM
To: 'Johnny L. Wales'; bac...@li...
Subject: RE: [BackupPC-users] A question about tapes


Correct.  Copy understands block devices, not character ones such as a
tape device.

The original question, I think, was how to do a backup?  If so, you need
to remember that the contents of the pc directories are adjusted.  The
filenames are mangled, the attributes (ownership and rights) are stored
and the files themselves are probably compressed.  Yes, you could dump
the entire pc directory to tape and recover it as well (with dump, tar,
etc) but you would still need BackupPC to convert the files.

<..snip...>