scsi tape manipulation

From: Dave (dspear99ca_at_yahoo.delete.com)
Date: 04/16/04 

Date: Fri, 16 Apr 2004 21:42:47 GMT

I recently added a DLT2000 to my Intel linux box:

Athlon 2400
2.4.25 kernel
Adaptec 2940UW SCSI adaptor

Okay, so I see it as /dev/st0 and /dev/nst0. I am used to administering
Solaris systems, where I would have /dev/rmt/0, /dev/rmt/0c /dev/rmt/0n, and
/dev/rmt/0cn. The "c" was to turn on hardware compression. I don't see any
such option mentioned in the st manpage for linux... is there a way to
toggle compression on or off? The reason: I am backing up several user dir
volumes that I'd like to (hardware) compress, then a large database backup
repository with lots of large, already-compressed files. I DO NOT want to
use hardware compression on compressed files as that tends to make them
bigger. The tape drive, when powered up, has hardware compression enabled.
I believe to change the default for this I need to flash the firmware, but
I'd much rather be able to toggle via software or, even better, via the use
of a specialized device driver.

Also, I note when I do:

# mt -f /dev/st0 stat
SCSI 2 tape drive:
File number=0, block number=0, partition=0.
Tape block size 0 bytes. Density code 0x19 (DLT 10GB).
Soft error count since last status=0
General status bits on (41010000):
 BOT ONLINE IM_REP_EN

that my density is listed at 0x19 or 10Gb capacity. There is a DLT-IIIXT
tape in it which should have 15/30Gb -/+ compression capacity. The drive
detects the tape correctly. Will I have problems writing more than 10Gb
onto this tape? If so, which conf file can I modify to change this value,
or will dump simply write until an EOT is detected?

Relevant Pages

  • Re: SBS Backup fails
    ... If the tape device supports hardware compression, ... This newsgroup only focuses on SBS technical issues. ...
    (microsoft.public.windows.server.sbs)
  • Re: software compression out
    ... The files are put directly to the tape without ... software compression, but hardware compressing. ... >>I found out that both software compression and hardware compression are ...
    (comp.unix.sco.misc)
  • Re: Server 2003 - NTBackup not compressing files to tape
    ... Backing up to DDS tape. ... NTBackup is told to use compression if possible. ... that your backup drive does NOT offer hardware compression. ...
    (microsoft.public.windows.server.general)
  • Re: DDS4 - hardware compression not working
    ... I was able to get 26gb on a tape. ... But with hardware compression, they recommend you not use software compression. ... I've found that hardware compression is not is good as software compression. ... Make a directory of a few large PostScript files and then keep on copying them recursively into new folders, doubling your the space used each time you copy. ...
    (comp.periphs.scsi)
  • Re: SBS Backup fails
    ... compression, but you found the hardware compression function is grayed out ... Business Backup Script.bks" /d "Small Business Server Backup created on ... This newsgroup only focuses on SBS technical issues. ...
    (microsoft.public.windows.server.sbs)