Hi John. No software compression is enabled in bacula. Files are basically 
compressible files, such as MS Office, engineer drawings, images, text files, 
etc. Just a fraction of them are compressed files (.ZIP and .RAR), not more 
than 5%.

Regarding your second comment I guess it could be the case and it is also worth 
of some more analysis. When bacula reaches the end of the tape, does it tell 
you or log the block where it has stopped? I know that a 'mt -f /dev/nst0 
status' would return the current block position, but I would like to know if 
bacula does it too. Also, is there a way to check how many total blocks the 
operating system or bacula are seeing on the tape? Regarding this last 
question, is tapeinfo's MinBlock/MaxBlock information reliable enough to 
conclude that this tape has a total of 16,777,215 blocks?

[root@br01 /usr/share/doc/mt-st-0.9b]# tapeinfo -f /dev/sg1
Product Type: Tape Drive
Vendor ID: 'IBM     '
Product ID: 'ULTRIUM-HH3     '
Revision: '93G7'
Attached Changer: No
SerialNumber: '1H10077966'
MinBlock:1
MaxBlock:16777215
SCSI ID: 6
SCSI LUN: 0
Ready: yes
BufferedMode: yes
Medium Type: 0x38
Density Code: 0x44
BlockSize: 0
DataCompEnabled: yes
DataCompCapable: yes
DataDeCompEnabled: yes
CompType: 0x1
DeCompType: 0x1
BOP: yes
Block Position: 0
[root@br01 /usr/share/doc/mt-st-0.9b]#

Cheers,
Rodrigo

-----Original Message-----
From: John Drescher [mailto:drescherjm AT gmail DOT com] 
Sent: Wednesday, September 01, 2010 3:44 PM
To: Rodrigo Ferraz
Cc: Brian Debelius; bacula-users
Subject: Re: [Bacula-users] RES: RES: LTO-3 tape not compressing data/premature 
end of tape space

> Yes John, they are LTO-3 tapes.
>
Is your data already compressed (.zip, .bz2, .7z, .mpeg ...)? Or is software 
compression enabled?

If not I am not sure. Bacula does not directly control the drive. It relies on 
the OS to tell it that the tape is full. Well actually this process is not even 
that clear. The streaming tape drive reports a write error when it can not fit 
a block on the tape. When bacula sees this error it checks that the last block 
was written successfully and then marks the tape full.

John

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