From owner-freebsd-questions Sun May 27 9:45:26 2001 Delivered-To: freebsd-questions@freebsd.org Received: from dan.emsphone.com (dan.emsphone.com [199.67.51.101]) by hub.freebsd.org (Postfix) with ESMTP id 92DF337B422 for ; Sun, 27 May 2001 09:45:24 -0700 (PDT) (envelope-from dan@dan.emsphone.com) Received: (from dan@localhost) by dan.emsphone.com (8.11.3/8.11.3) id f4RGjKh09131; Sun, 27 May 2001 11:45:20 -0500 (CDT) (envelope-from dan) Date: Sun, 27 May 2001 11:45:20 -0500 From: Dan Nelson To: Felix Hernandez Cc: Bill Moran , freebsd-questions@FreeBSD.ORG, Ian Dowse Subject: Re: Slower tape drive when compression off Message-ID: <20010527114520.A5559@dan.emsphone.com> References: <20010527160722.3092.qmail@web9501.mail.yahoo.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20010527160722.3092.qmail@web9501.mail.yahoo.com> User-Agent: Mutt/1.3.18i X-OS: FreeBSD 5.0-CURRENT Sender: owner-freebsd-questions@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG In the last episode (May 27), Felix Hernandez said: > Yes!!! Right on the nail! It was a buffer size problem. > > root@oberon $$$ mt comp off > root@oberon $$$ dd if=junk of=/dev/rsa0 bs=10k > 51200000 bytes transferred in 22.686704 secs (2256829 bytes/sec) > root@oberon $$$ dd if=junk of=/dev/rsa0 bs=64k > 51200000 bytes transferred in 9.491773 secs (5394145 bytes/sec) > root@oberon $$$ dd if=junk of=/dev/rsa0 bs=256k > 51200000 bytes transferred in 9.497948 secs (5390638 bytes/sec) BTW, the last two results are the same because FreeBSD currently has a 64K limit on SCSI I/O size. Your 256K write was internally split into four 64k ones. -- Dan Nelson dnelson@emsphone.com To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message