Gene,
Thanks for your input. I have seen your commentary on this issue on the list before, but had
neglected to recall the details.
I tried it, and it didn't seem to work any magic. Here is my session with the
amtapetype run at the end.
$ sudo mt -f /dev/nst1 rewind
$ sudo dd if=/dev/nst1 bs=512k count=1 of=tape-header
1+0 records in
1+0 records out
524288 bytes (524 kB) copied, 0.00732916 s, 71.5 MB/s
$ ls -l tape-header
-rw-r----- 1 root sysadmin 524288 Aug 4 12:06 tape-header
$ more tape-header
AMANDA: TAPESTART DATE 20170801124200 TAPE amtapetype-1158747886
^L
$ sudo mt -f /dev/nst1 rewind
$ sudo mt -f /dev/nst1 compression 0
$ sudo mt -f /dev/nst1 defcompression 0
$ sudo dd if=tape-header bs=512k count=1 of=/dev/nst1
1+0 records in
1+0 records out
524288 bytes (524 kB) copied, 24.7811 s, 21.2 kB/s
$ sudo mt -f /dev/nst1 rewind
$ sudo tapeinfo -f /dev/sg15
Product Type: Tape Drive
Vendor ID: 'IBM '
Product ID: 'ULTRIUM-HH7 '
Revision: 'G9Q1'
Attached Changer API: No
SerialNumber: '10WT039810'
MinBlock: 1
MaxBlock: 8388608
SCSI ID: 1
SCSI LUN: 0
Ready: yes
BufferedMode: yes
Medium Type: 0x78
Density Code: 0x5c
BlockSize: 0
DataCompEnabled: no
DataCompCapable: yes
DataDeCompEnabled: yes
CompType: 0xff
DeCompType: 0xff
BOP: yes
Block Position: 0
Partition 0 Remaining Kbytes: -1
Partition 0 Size in Kbytes: -1
ActivePartition: 0
EarlyWarningSize: 0
NumPartitions: 0
MaxPartitions: 3
$ sudo amtapetype -f -c -b 512k /dev/nst1
Checking for FSF_AFTER_FILEMARK requirement
Applying heuristic check for compression.
Wrote random (uncompressible) data at 207,231,278.163934 bytes/sec
[added commas]
Wrote fixed (compressible) data at 280,913,510.4 bytes/sec
[aligned for comparison]
Compression: enabled
$
On 8/3/17 7:26 PM, Gene Heskett wrote:
On Thursday 03 August 2017 15:59:00 Will Aoki wrote:
On Mon, Jul 31, 2017 at 04:37:37PM -0400, Chris Hoogendyk wrote:
Here is my latest attempt, working with a new, never been loaded,
LTO7 tape. I should note that I have a page in my server notebook
from July 2014 showing almost this exact sequence of commands when
setting up my LTO6 library.
Quite a high percentage of the modern tape drives, will, after a rewind,
if asked for a read, will reread the tape header, see that compression
is enabled, and will very helpfully (not!) re-enable it. I have in the
past, read out the amanda header, the first VISIBLE 32k block on the
tape, rewound the tape, turn the compression off and instantly, before
the drive is moved again, rewrite that 32k amanda header block, which
then locks the compression off until such time as you rewind it,
re-enable it and write something to lock it back on.
Bottom line is that tapeinfo tells me compression is off, it's a new
tape, then amtapetype tells me compression is on.
Tapeinfo IIRC gets that info from the drives firmware without moving the
tape.
amtapetype actually reads the tape, moving it to determine that. Moving
it resets it by reading the tapes hidden header.
So rewind it
dd the amanda header out to a scratch file
rewind it
turn the compression off
dd that scratch file back to the tape
Then you should have agreement between Tapeinfo and amtapetype, saying
the compression is off.
If you are recycling tapes, do the above to each tape you insert until
you have done this little routine with every tape destined to be
inserted into this drive. But do not do it ahead of its scheduled re-use
as that invalidates the backup you might need before the next scheduled
amanda run if something upchucks between doing it, and the run that
re-uses it.
I wasn't able to get compression turned off on the LTO-7 drive in my
Quantum SuperLoader 3. I ended up deciding to leave compression on,
as it didn't seem to do any harm in my testing.
My drive:
Product Type: Tape Drive
Vendor ID: 'IBM '
Product ID: 'ULTRIUM-HH7 '
Revision: 'FA17'
Attached Changer API: No
SerialNumber: '10WT------'
MinBlock: 1
MaxBlock: 8388608
SCSI ID: 23
SCSI LUN: 0
Ready: yes
BufferedMode: yes
Medium Type: 0x78
Density Code: 0x5c
BlockSize: 0
DataCompEnabled: yes
DataCompCapable: yes
DataDeCompEnabled: yes
CompType: 0xff
DeCompType: 0xff
BOP: yes
Block Position: 0
Partition 0 Remaining Kbytes: -1
Partition 0 Size in Kbytes: -1
ActivePartition: 0
EarlyWarningSize: 0
NumPartitions: 0
MaxPartitions: 3
My tapetype:
#Checking for FSF_AFTER_FILEMARK requirement
#Applying heuristic check for compression.
#Wrote random (uncompressible) data at 92327868.852459 bytes/sec
#Wrote fixed (compressible) data at 165647058.823529 bytes/sec
#Compression: enabled
#Writing one file to fill the volume.
#Wrote 6015744049152 bytes at 86102 kb/sec
#Writing smaller files (60157427712 bytes) to determine filemark.
define tapetype lto-7 {
# Couldn't seem to get compression disabled...
comment "Created by amtapetype; compression enabled"
length 5874750048 kbytes
filemark 12 kbytes
speed 86102 kps
blocksize 32 kbytes
part_size 200G
part_cache_type memory
part_cache_max_size 48G
}
Cheers, Gene Heskett
--
---------------
Chris Hoogendyk
-
O__ ---- Systems Administrator
c/ /'_ --- Biology & Geosciences Departments
(*) \(*) -- 315 Morrill Science Center
~~~~~~~~~~ - University of Massachusetts, Amherst
<[email protected]>
---------------
Erdös 4
