Attila Bogár wrote:
Dear Amanda Users,
I have some question regarding tape blocksizes.
I inherited an amanda system with default (32k?) blocksize.
Then by doing some testing with dd bs=nk I found, that the Quantum
LTO-4 tape drive honours the 128k blocksize with the fastest speed.
I have the following paramers set in amanda.conf:
--- 8< ---
define device top_drive {
tapedev "tape:/dev/nsa1"
device-property "BLOCK_SIZE" "131072"
}
define device bottom_drive {
tapedev "tape:/dev/nsa0"
device-property "BLOCK_SIZE" "131072"
}
tpchanger "chg-multi:{top_drive,bottom_drive}"
define tapetype LTO4 {
length 780 gbytes
filemark 3273 kbytes
speed 70 mps
blocksize 128 kbytes
}
--- 8< ---
As you can see there's BLOCK_SIZE device property, then there's
blocksize parameter for the tapetype.
Additionally the block size can be via 'mt -f /dev/nsa0 blocksize n'
(on FreeBSD).
Question 1)
If I set the blocksize to 128k via mt, then I can't read the tapes.
Do I need to set this up directly via mt.
If so, then do I have to re-initialize old tapes? (amrmtape, mt erase,
amlabel)?
Don't do that, the tape drive must be in variable block size.
Question 2)
Are both settings in amanda.conf required or one of them is superfluous?
The device_property BLOCK_SIZE have priority if it is set.
Question 3)
Amanda inserts a 32k header, when writing a dump about the dump's meta
data.
How is this affected, when using an offset other than 32k?
What will be the offset of the real (.tar) data?
The header is the first block, the data start on the second block.
Jean-Louis
