Re: [Networker] Time differences in writing 1Gb

Tim,

I realized that , thats why the program starts with preparing 1 block of data
like cat /dev/random | gzip . The program thens reads only 1 block of 128 k
into a buffer. Iit thens starts writing this one block repeatadly to the
device until an error occurs. Meanwhile reporting the time differences every
1 GB. After writing it then rewinds the tape and starts reading to verify
that it can read till the same end of the data where the writing stopped (of
failed).

Maarten



On Monday 19 July 2004 20:31, Tim Mooney wrote:
> In regard to: [Networker] Time differences in writing 1Gb, Maarten Boot...:
> > On some tapes (not all) I see some interesting time differences on an
> > otherwise idle machine
> >
> > Hardware used:
> >
> > Sun E450 with 2 400 Mhz CPU, 1 GB mem
> > scsi card:  LSILogic LSI22320-R
> > Exabyte 110L with IBM ULTRIUM2 drives (firmware: 38D0)
> >
> > data written is a 128k block of gzipped random data from /dev/random
>
> Couldn't this be more a factor of what's coming out of /dev/random than
> the tape drive(s) themselves?  If your machine is idle, what you're
> getting out of /dev/random could vary widely during several runs.
>
> I recommend you take real local data and repeat the tests several times.
> This will still be influenced by caching, but at least if you repeat the
> tests on real data, you know you're always getting the same source data.
>
> Tim
> --
> Tim Mooney                              mooney AT dogbert.cc.ndsu.NoDak DOT 
> edu
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--
Maarten Boot,
Compuware Europe B.V.
Hoogoorddreef 5
1101 BA Amsterdam

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