Date: Sat, 26 May 2001 22:07:33 -0500 From: Dan Nelson <dnelson@emsphone.com> To: Felix Hernandez <felix_hdez@yahoo.com> Cc: Bill Moran <wmoran@iowna.com>, freebsd-questions@FreeBSD.ORG Subject: Re: Slower tape drive when compression off Message-ID: <20010526220733.A21021@dan.emsphone.com> In-Reply-To: <20010526225855.16007.qmail@web9506.mail.yahoo.com> References: <20010526225855.16007.qmail@web9506.mail.yahoo.com>
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In the last episode (May 26), Felix Hernandez said: > root@oberon $$$ mt comp off > root@oberon $$$ dd if=junk of=/dev/rsa0 bs=10k > 51200000 bytes transferred in 20.322325 secs (2519397 bytes/sec) > > root@oberon $$$ mt comp on > root@oberon $$$ dd if=junk of=/dev/rsa0 bs=10k > 51200000 bytes transferred in 12.665153 secs (4042588 bytes/sec) That's really weird. A 10k blocksize is pretty small for DLT, though (it's the default tar blocksize). Try with a 64K blocksize, and tell us your CPU speed. A DLT8000 should be able to stream data at 6MB/sec native, 12MB/sec if the data is compressible. Maybe your hardware isn't capable of sending data to the DLT fast enough to keep it streaming. Also see what a "dd if=/dev/zero of=/dev/rsa0 bs=64k" does; maybe your disks are the bottleneck. Turn compression off for this test, of course :) -- Dan Nelson dnelson@emsphone.com To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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