Veritas-bu

FW: [Veritas-bu] LTO Barcode Labels that end in L1 on LTO2 tapes

2004-12-01 05:24:02
Subject: FW: [Veritas-bu] LTO Barcode Labels that end in L1 on LTO2 tapes
From: william.d.brown AT gsk DOT com (william.d.brown AT gsk DOT com)
Date: Wed, 1 Dec 2004 10:24:02 +0000
Don't forget that there are 3 players in the game:

The robot with the barcode scanner.
The drive.
NetBackup.

Taking the robot first, it scans the barcode and uses it to tell what kind 
of tape it is.  Our StK libraries and I guess most others now use those 
last digits to tell LTO1 from LTO2 etc.   If you looks at the library GUI 
it tells you what kind of tape is in each slot based on that information.

Taking Netbackup next, it believes what it is told by the robot about what 
the barcode is, but that no longer includes the trailing information (the 
L1, L2 etc).  I know some libraries pass it all on, and then you need to 
write your own barcode masking rules; ours do not.  So you have to write 
barcode rules that use the leading characters of the barcode to determine 
the pool, media type etc.  So you must have different *leading* characters 
if Netbackup is to decide some are HCART and some are HCART2 etc.

NetBackup also knows the type of each drive (HCART, HCART2 etc).  It will 
not attempt to put a tape in a drive of a different type.  Note that it 
has *no support* for backwards read, let alone backwards write, 
compatibility.   I hear that folk are finding that LTO1 tapes in an LTO2 
drive do benefit from big speed increases (but obviously not extra 
capacity!).   This is a real pain as it is common to swap out older drives 
with newer 'BRC' drives...but NetBackup does not help this.

Lastly the drive - LTO drives can detect from the Cartridge Memory (CM) 
what kind of media it is - so it can tell a cleaning tape from a data 
tape, and LTO1 from LTO2 etc.   An LTO2 drive is perfectly happy to be 
loaded with an LTO1 tape.   If you load a cleaning tape it did not ask 
for, it throws it out without using it (well our IBM drives do).   If you 
barcode a cleaning tape as a data tape (yes it happens, don't buy black 
cleaning tapes) Netbackup will load it and wonder why it does not come on 
line, and down the drive....

So back to the question:

Is there a problem with putting LTO Barcode Labels
that end in L1 on LTO2 tapes? 

No, it is OK if it does what you want.   The robot will think they are 
LTO1 but I don't think that matters.   The leading part of the barcode and 
your barcode rules will determine if NetBackup thinks they are HCART1 or 
HCART2 - you must make sure they are made to be HCART2.   NetBackup will 
then happily use them in your LTO2 drives.  If your library also has LTO1 
drives NetBackup will not load them into those drives (right answer).  If 
you have LTO1 drives you want to go on using you must have LTO1 tapes with 
the leading part of the barcode different and the barcode rules set to 
make them HCART.

I hope this will allow you to do what you want.

William D L Brown



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