Error reading Amanda header: block size too small

Resolution of error reading Amanda header for block size too small

Issue Symptoms 

taper: slot 1:Error reading label: Error reading Amanda header: block size too small, autolabel disabled 

Issue Description

The block size Amanda uses to read the blocks on the tape is smaller than the size of the blocks of data already on the tape: the read block size is "too small" to read the tape's blocks. In the case of the error shown above, Amanda is trying to read the Amanda label on a tape but is unable to read it because the size of the tape's blocks is larger than Amanda's minimum block size of 32k.


The tape device will need its block size set to be either 32k or larger or 0 to allow Amanda to set the block size automatically. The method for doing this depends on the tape drive and its firmware. Consult the tape drive manufacturer's documentation for the steps to change the minimum block size on the device.

Use the mt command to check the block size setting on a tape drive: 

$ mt -f /dev/nst0 status
SCSI 2 tape drive:
File number=0, block number=0, partition=0.
Tape block size 0 bytes. Density code 0x46 (LTO-4).
Soft error count since last status=0
General status bits on (41010000):

In this example the Tape block size is set to 0, or variable.

Most tape drives will accept commands to change the block size setting via the mt command, but this depends on the drive firmware. The defblksize and setblk size can be used to configure the block size the tape drive will so. Setting both values to 0 will allow Amanda to control the size.

$ mt -f /dev/nst4 defblksize 0
$ mt -f /dev/nst4 setblk 0