On Thursday 19 June 2003 14:09, Ean Kingston wrote:
>> -----Original Message-----
>>
>> On Thursday 19 June 2003 11:51, Ean Kingston wrote:
>> >I couldn't find this one in the list archives, so here it is.
>> >
>> >I'm using 40GB DLT tapes (according to the label). Despite what
>> > the comment produced says, I used the non-compressed device. I
>> > didn't give it an estimate for the tapesize.
>> >
>> >Writing 256 Mbyte   compresseable data:  34 sec
>> >Writing 256 Mbyte uncompresseable data:  105 sec
>> >WARNING: Tape drive has hardware compression enabled
>> >Estimated time to write 2 * 1024 Mbyte: 840 sec = 0 h 14 min
>> >wrote 1102644 32Kb blocks in 3372 files in 21817 seconds (short
>> > write) wrote 1101228 32Kb blocks in 6756 files in 29828 seconds
>> > (short write) define tapetype HP-DLT1e {
>> >    comment "just produced by tapetype prog (hardware compression
>> > on)" length 34499 mbytes
>> >    filemark 13 kbytes
>> >    speed 1399 kps
>> >}
>>
>> And it appears the hardware compressor being on cost you 5.5 gigs.
>> The various 'tapetype' programs all use the output of /dev/urandom
>> as the data source, and the output of /dev/urandom is not
>> compressible, and will in fact grow by about the percentage you
>> see above in being passed thru the hardware compressor.
>>
>> As others have noted Ean, you can turn it off, but this must be
>> done for every new tape that's inserted as the recognition phase
>> of the drive will turn it back on when the tapes are changed. 
>> Such info as how to turn it on/off should be on the drive makers
>> web page.  To your vendor its obviously not a very high priority
>> to obtain that info for you else he would have fired up a browser
>> and found it on the spot.
>
>I'm using Solaris and, according to the documentation, it should not
> be using hardware compression unless I specify the 'compress'
> device (/dev/rmt/0cn) as opposed to the one I did use
> (/dev/rmt/0n). If what you say it true there is some way to force
> HW compression for the tape drive regardless of what the OS wants.

I'll leave that pronouncement to the Sol experts here, like Jon 
LaBadie.

-- 
Cheers, Gene
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Copyright 2003 by Maurice Eugene Heskett, all rights reserved.