tar doesn't adjust block count

[SZYMCZAK Jérémy - ENTE Val . /Direction Stratégie et Développement/Politique informatique]

good morning

i try to use mt / tar commands to backup several new servers (Ubuntu 18.04 LTS, kernel 4.15.0-112-generic, Dell T630 and 640) on their LTO6 tape drives.

i try to log my backed-up files with block count, to make file restoring faster ('tar --block-number').

Thus, i've activated the 'mt stoptions scsi2logical' to activate block count.

Then, when i change the 'mt setblk' option on the same server, the number of saved blocks increases or decreases ('mt eod' + 'mt tell') -> OK

But when i change neither the 'tar -b', nor the 'tar --record-size' options, block count on my tar log file is still the same. No compression activated.

Anything wrong with tar block count ?

thanks

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Jérémy SZYMCZAK
École nationale des techniciens de l’équipement
Direction de la stratégie et du développement
Politique informatique et systèmes d'informations
Tél : 03 27 23 73 95