On Tuesday 30 April 2013 21:34:11 Debra S Baddorf did opine:
> 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.
Sorry to break that bubble, but it has been my experience that if your
rewind the tape, it will re-read that hidden header and turn compression
back on regardless.
The only solution I have found that worked was to
rewind
read the first 32k out to a scratch file
rewind
turn the compression off
write that scratch file back to the tape
rewind
check compression status, it finally should be off.
If you give the drive an excuse to read the header on the tape by rewinding
BEFORE you write anything, you will appear to be in a loop, and the only
way out is rewind, set the compression off and immediately write that
header scratch file back to the tape.
> 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 <Jean-
francois.malo...@bic.mni.mcgill.ca> wrote:
> >> * Abilio Carvalho <abilio.carva...@bbp.ch> [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 <Jean-
francois.malo...@bic.mni.mcgill.ca> wrote:
> >>>> * Abilio Carvalho <abilio.carva...@bbp.ch> [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
<abilio.carva...@bbp.ch> 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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Cheers, Gene
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