As I understand it (from reading here) there is something set ON EACH TAPE
which
turns the compression back on. I've even run the amtapetype test on a brand
new tape,
and it turns the compression back on.
The fix is to overwrite that "bit" or whatever it is. Like this:
mt -f /dev/nst2 comp off
mt -f /dev/nst2 compression off
dd of=/dev/nst2 if=/dev/zero bs=32k count=3272 #or 32728
then rewind and try the amtapetype again. This time it will tell you that
compression
finally off. And you'll get a better value for the tapetype, too.
I do this now for each new tape (and one for the old tapes too). THEN the
compress
will stay off, once the tape stops turning it back on.
I think. ;)
Deb Baddorf
Fermilab
On Apr 30, 2013, at 10:09 AM, Abilio Carvalho wrote:
> OK, this is odd. Here's what I get, can you guys help me figure this out?
>
> $ mtx -f /dev/sg2 status
> Storage Changer /dev/sg2:1 Drives, 8 Slots ( 0 Import/Export )
> Data Transfer Element 0:Full (Storage Element 2 Loaded):VolumeTag = ABR832L6
>
> Storage Element 1:Full :VolumeTag=ABR833L6
> Storage Element 2:Empty
> Storage Element 3:Empty
> Storage Element 4:Empty
> Storage Element 5:Empty
> Storage Element 6:Empty
> Storage Element 7:Empty
> Storage Element 8:Empty
>
> $ tapeinfo -f /dev/st0
> Product Type: Tape Drive
> Vendor ID: 'HP '
> Product ID: 'Ultrium 6-SCSI '
> Revision: '22CW'
> Attached Changer API: No
> SerialNumber: 'HU1246T9JH'
> MinBlock: 1
> MaxBlock: 16777215
> SCSI ID: 0
> SCSI LUN: 0
> Ready: yes
> BufferedMode: yes
> Medium Type: Not Loaded
> Density Code: 0x5a
> BlockSize: 0
> DataCompEnabled: no
> DataCompCapable: yes
> DataDeCompEnabled: yes
> CompType: 0x1
> DeCompType: 0x1
> BOP: yes
> Block Position: 0
> ActivePartition: 0
> EarlyWarningSize: 0
> NumPartitions: 0
> MaxPartitions: 3
>
> $ amtapetype -c -f /dev/st0
> perl: warning: Setting locale failed.
> perl: warning: Please check that your locale settings:
> LANGUAGE = (unset),
> LC_ALL = (unset),
> LC_CTYPE = "UTF-8",
> LANG = "en_US.UTF-8"
> are supported and installed on your system.
> perl: warning: Falling back to the standard locale ("C").
> Checking for FSF_AFTER_FILEMARK requirement
> Applying heuristic check for compression.
> Wrote random (uncompressible) data at 73472726.7096774 bytes/sec
> Wrote fixed (compressible) data at 101229090.133333 bytes/sec
> Compression: enabled
>
>
> NOTE: I mistyped my last email. I ran mt on /dev/st0, not sg2. this email has
> the correct devices.
>
> Thanks for the help so far, Jean-François
>
>
>
> On Apr 30, 2013, at 4:51 PM, Jean-Francois Malouin
> <[email protected]> wrote:
>
>> * Abilio Carvalho <[email protected]> [20130430 10:36]:
>>> sorry, no I hadn't disabled compression. Today I installed mt-st and
>>> following the wiki I ran:
>>>
>>> mt -f /dev/sg2 compression 0
>>> mt -f /dev/sg2 defcompression 0
>>>
>>> but when I now run amtapetype it still tells me:
>>>
>>> Applying heuristic check for compression.
>>> Wrote random (uncompressible) data at 73376008.2580645 bytes/sec
>>> Wrote fixed (compressible) data at 101095833.6 bytes/sec
>>> Compression: enabled
>>>
>>> how can I make sure hardware compression is off?
>>
>> Make sure you have a tape loaded.
>> Replace the tape drive scsi generic device sgX accordingly.
>> In case of LTO5 here is what I get:
>>
>> ~# tapeinfo -f /dev/sgX
>> Product Type: Tape Drive
>> Vendor ID: 'HP '
>> Product ID: 'Ultrium 5-SCSI '
>> ...
>> DataCompEnabled: yes
>> DataCompCapable: yes
>> DataDeCompEnabled: yes
>> ...
>>
>> ~# mt-st -f /dev/nst0 defcompression 0
>> ~# tapeinfo -f /dev/sgX
>> ...
>> DataCompEnabled: no
>> DataCompCapable: yes
>> DataDeCompEnabled: yes
>>
>> hth,
>> jf
>>
>>>
>>> On Apr 17, 2013, at 6:40 PM, Jean-Francois Malouin
>>> <[email protected]> wrote:
>>>
>>>> * Abilio Carvalho <[email protected]> [20130417 10:19]:
>>>>> Well, since noone answered, I had to run amtapetype, so here it is if
>>>>> anyone else needs it:
>>>>>
>>>>> define tapetype LTO6 {
>>>>> comment "Created by amtapetype; compression enabled"
>>>>> length 2442818848 kbytes
>>>>> filemark 1806 kbytes
>>>>> speed 74006 kps
>>>>> blocksize 32 kbytes
>>>>> }
>>>>
>>>> Hmmm, speed look way off. Native speed is 160MBs for LTO6...
>>>> Did you disable hardware compression before running amtapetype?
>>>> Also, you might want to test with larger blocksize, for LTO5 I use 2MB
>>>> with good results....
>>>>
>>>> hth,
>>>> jf
>>>>
>>>>>
>>>>>
>>>>> On Apr 16, 2013, at 3:24 PM, Abilio Carvalho <[email protected]>
>>>>> wrote:
>>>>>
>>>>>> Hi, just a quick question, does anyone have a tape type for an LTO6
>>>>>> drive? (Ideally an HP Ultrium 6 SCSI)
>>>>>>
>>>>>> Thanks
>>>>>> Abilio
>
>
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