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Very slow SCSI tape drive with cygwin/Win2kPro


Howdy,

I am having problems with very slowing reading from an Ultrium 1 SCSI 
tape drive (100GB capacity).  With the current version of cygwin (and 
older) the drive is reading less than 200KB/sec using tar, dd and cpio.  
The drive is capable of reading 16MB/sec.  There are no problems with 
Win2k's NTBackup and an evaluation version of the MKS Tool Kit so this 
appears to be a problem with cygwin.

The simplest way to see the problem is insert an Ultrium tape - say with 
the block size 16KB and run these commands with an otherwise quiescent 
system:

 mt -f /dev/nst0 setblk 8192
 tar -tf /dev/nst0 -b 32

and the SCSI bus activity light flashes about 8 times per second.

The hardware is a 1.4GHz AMD Athlon with 512MB memory, Adaptec 2940UW 
SCSI controller with three SCSI disks and the Ultrium tape drive.

cygwin is the current version and win2k Pro has all the current patches 
according to Windows Update.

Block size does not seem to be a factor.  I've tried 8k, 16k and 32k 
(over 32k doesn't work for some reason).

I've searched the on the web, the manuals, the FAQ and the cygwin list 
archive.

Just in case it is helpful I've included the output from
"mt -f /dev/st0 status 3" after rebooting at the end.

 Thanks in advance,
 Bill


Administrator@zoe ~
$ mt -f /dev/st0 setblk 32768

Administrator@zoe ~
$ mt -f /dev/st0 status 3
drive type       :       01 (Unknown type of tape device)
tape capacity    : 102629376 KB          remaining        :  8861696 KB
current file     :        0             active partition :        0
current block    :        0             cur logical block:        0
General status bits on (45030000):
 BOT WR_PROT ONLINE IM_REP_EN HW_COMP
min block size   :        2             max block size   :    32768
def block size   :    32768             cur block size   :    32768
density code     :       00 (default)
EOT zone size    :        0
Drive(r) Capabilities:
----------------------
fixed length blocks        : yes        var length blocks          : yes
set block size             : yes        fixed partitioning         : no
select partitioning        : no         initiator partitioning     : no
get logical blockno        : yes        logical block spacing      : yes
get absolute blockno       : yes        absolute block spacing     : yes
logical block immediate    : yes        absolute block immediate   : yes
relative block spacing     : yes        backward spacing           : yes
immediate rewind           : yes        fast EOM spacing           : yes
immediate spacing          : no         write marks immediate      : yes
filemark spacing           : yes        write filemarks            : yes
write long filemarks       : no         write short filemarks      : no
report setmarks            : no         setmark spacing            : no
write setmarks             : no         set report setmarks        : no
sequential filemarks       : no         sequential setmarks        : no
load and unload            : yes        un/load immediate          : yes
lock and unlock            : yes        un/lock immediate          : no
tape retension             : no         retension immediate        : no
erase on bop only          : no         erase immediately          : yes
long erase                 : yes        short erase                : yes
sw ejects media            : yes        report write protection    : yes
report EOT warn size       : yes        set EOT warn size          : no
data padding               : no         set data padding           : no
returns capacity           : yes        returns remaining          : yes
hw error correction        : no         set hw error correction    : no
hw compression             : yes        set compression            : yes
set comp. on bop only      : no         report cleaning request    : no

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