>From what I have observed, and others on the list have told me, Amanda will
always try and fill the tape completely even if it knows it has written say
30GB, to a tapetype that is 40GB, and it sees the upcoming dump estimate as
20GB. By fill completely I mean write until the tape drive reports the end
of the tape (EOT). I would like to see an option in amanda.conf to have it
honour(honor) the estimates and tapetype values and rewind and request a
tape change to the next tape in this case. In my case I have a changer and
this would reduce my backup time, and tape drive wear, as the time wasted in
putting the first 10GB onto tape before it runs out could be avoided in this
case since it has to re-write the 10GB all over again after changing to the
next tape in the changer.
The estimate would work well in my case as I have hardware compression
turned off on the drive and am using software compression in Amanda so the
number I spec. in tapetype, as long as it is slightly smaller than an actual
tape should always be the correct size that will go to tape.
The other thing to be aware of that I seem to have stumbled across is
related to overflowing a tape and dumps that are written directly to tape as
there is not enough holding space for them. In this case Amanda does not
appear to retry the next tape in the changer if this happens. I do not know
for sure if this is by design or a bug yet. I am still looking through the
code.
Now re: your tape. Amanda itself is not trying to rip the tape off the end
of the spool. If the drive is doing this each time then there is a problem
with the tape drive mechanism. It is a perfectly normal condition for a
drive to use up all tape and reach the end. Maybe this was just a
manufacturers defect in that tape, maybe the drive requires adjustment ?
Scott...
Scott R. Burns
NETCON Technologies Inc.
Suite 135 - 4474 Blakie Road
London, Ontario, Canada
N6L 1G7
Voice: +1.519.652.0401
Fax: +1.519.652.9275
-----Original Message-----
From: owner-amanda-users AT amanda DOT org
[mailto:owner-amanda-users AT amanda DOT org]On Behalf Of Dan Brown
Sent: Saturday, August 06, 2005 5:07 AM
To: amanda-users AT amanda DOT org
Subject: TapeTypes definition affecting wear?
The system we have setup at work have all backups, regardless of whether
or not the tape drive is free, sent to a network holding disk before
being flushed to tape to avoid the problem of "I just used a 40GB tape
to backup 2GB of data.... too bad I can't append new data to the tape".
The only device between the holding disk machine and the server the
tape drive is attached to is a switch, and between the high capacity
ethernet link and the fine tuning to amanda's parameters to avoid the
"shoe shining" behavior of the tape drive, it works pretty well.
That's just some background info but not the question I am looking for
an answer to here.
I just spent the last two hours manually unreeling half a kilometer of
broken DLT-IV tape off of a DLT1 drive and was about to throw a new tape
back into the drive (after resetting it's feeder/tape puller, etc) to
resume backup flushes when it occured to me that I rarely ever saw a
flush report where there were X filesystems flushed, with no errors.
Typically, in the notes section of the flush (or backup) report, there
is a line saying:
taper: tape gimpFull02 kb 35794048 fm 14 writing file: No space left
on device
And in the list of dump definitions (in this case, a partition) it will
list the partition as failed.
gimp sda5 0 N/A 0 -- N/A N/A FAILED ----
So, will amanda always try to stuff as much as possible onto a tape
until it reaches the end of the tape or will it actually estimate
whether it can fit the next backed up partition/directory definition
onto the tape? If I used ammt or mt to wind to the end of the tape and
read a few blocks, would I see data from the failed disk being backed up?
If the tape drive actually reaches the end of the tape before it stops
it would explain why it appears the spool of tape I pulled off was from
the very end of the reel and there appears to be no tape left in the
cartridge.
My tapetype definition looks like this:
define tapetype DLT4 {
comment "DLTtapeIV on a Quantum DLT1 drive"
length 42949 mbytes # 40 Gig tapes
filemark 4000 kbytes # I don't know what this means
speed 2814 kbytes # 2.5 Mb/s - nice and easy! :P
}
So if I define the tape to be larger than it really is (maybe I should
define it as a 35GB tape instead?), will amanda attempt to yank the end
of the tape out of the cartridge every time or is there enough force to
normally do so anyways? The drive is a Quantum DLT1 stuck inside a
Lacie enclosure, according to Quantum specs the tapes should be
considered as 40GB.
Do tapetype definitions affect this sort of thing at all or should I
just consider this the premature death (a little over a year old) of a tape?
---
Dan Brown
dcmbrown AT shaw DOT ca
monkeypants AT shaw DOT ca
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