Re: New tapetype
2003-02-04 10:44:58
Gene,
Thanks - I was wondering about that. I'm using /dev/nst0 - do I need use a different device to avoid compression? I'm really new to this - thanks for the help. I'm posting a follow up with some SCSI issues I had in setup this morning...
-John
Gene Heskett <gene_heskett AT iolinc DOT net> wrote:
On Tuesday 04 February 2003 07:37, John Cunningham wrote: >Hey guys - just wanted to post this. It's a tapetype for IBM > DDS-4 Autoloader running 150M 20/40 GB DAT tape... > >define tapetype XLIX { > comment "IBM DDS-4 120 / 240 GB Autoloader" > length 16564 mbytes > filemark 0 kbytes > speed 2282 kps >}
John, that's supposed to be a 20 gig tape, so it looks as if the hardware compression was on when you ran tapetype. That will give you somewhat low estimates for the size as tapetype uses /dev/urandom as the data source, and the output of /dev/urandom will generally overpower the hardware compressors and cause the data to actually be expanded a bit. So the drive actualy wrote more data than tapetype fed it, leading to an early EOT finding in terms of the amount of data sent.
If thats the case,!
this is a dds tape, and you will probably need to go back up the list here and see how to remove compression from *that* tape from one of my previous posts on the subject.
In any event, gzip can beat the hardware compressors 90% of the time, so generally speaking, if the server has the horsepower to do the compression, you should let it do so for those disklist entries that will compress. About 1/3rd of my disklist won't compress, its archives and such that already are, but the rest do really well, so the average output size here is about 40% of the input size.
-- Cheers, Gene AMD K6-III@500mhz 320M Athlon1600XP@1400mhz 512M 99.23% setiathome rank, not too shabby for a WV hillbilly
Do you Yahoo!?
Yahoo! Mail Plus - Powerful. Affordable. Sign up now
|
|
|