Date: Mon, 30 Jul 2001 02:22:06 +0200 From: "Jose M. Alcaide" <jose@we.lc.ehu.es> To: mjacob@feral.com Cc: scsi@FreeBSD.ORG Subject: Re: DLT 4000 throughput and cstream Message-ID: <3B64A8AE.39629CBE@we.lc.ehu.es> References: <Pine.BSF.4.21.0107281231100.13594-100000@beppo>
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Matthew Jacob wrote: > > [ -hardware trimmed- Only one list is needed ] Hum. I sent the message to -hardware _only_... > > > KB/t tps MB/s > > > 60.59 22 1.31 > > > 60.59 22 1.31 > > > 61.05 22 1.31 > > > 60.62 22 1.32 > > > 60.59 22 1.31 > > > ... > > This is about half the speed you should expect. > > Testing with dump, w/wo cstream, is not helpful. You need to test with a > non-zero data generator: You are right. I also tested "cstream -i - ..." and "dd if=/dev/urandom ...", with similar result. Anyway, I am interested in the dump case, since it is the actual application. BTW, I also tested dumping the same filesystem to a file on another disk, achieving 7-8 MB/s while dump was in pass IV. > yorp.feral.com > tape_pattern_tester > tape_pattern_tester: [ -v ] [ -b blksize ] [ -r blocks per file ] [ -n > number-of-files ] -f no-rewinding-tape-drive > yorp.feral.com > tape_pattern_tester -v -b 32k -r 1000 -n 5 -f /dev/nsa0 > .......Rewind Tape > ........Write Pass > EOT at File 4 Record 1000 Offset 32768 (163840000 total bytes written) > Elapsed Seconds: 60; Data Rate: 2.6MB/s > .......Rewind Tape > .........Read Pass > EOT at File 5 Record 0 Offset 0 (163840000 total bytes read) > Elapsed Seconds: 72: Data Rate: 2.16667MB/s Hum... 32KB block size... is that size appropriate for DLTs? Some people recommend big block sizes, but I think they are confusing the device block size with the size of an intermediate buffer between the input and output streams. DLTs seem to accept very big block sizes; however, I cannot see any improvements for block sizes bigger than 32-64KB, provided there is a big intermediate buffer, of course. Hey, that "tape_pattern_tester" utility seems interesting. Where could I find it? Did you write it? Thanks, -- JMA ****** Jose M. Alcaide // jose@we.lc.ehu.es // jmas@FreeBSD.org ****** ** "Beware of Programmers who carry screwdrivers" -- Leonard Brandwein ** To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-scsi" in the body of the message
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