Date: Wed, 22 Jan 2003 20:01:35 -0800 From: "Dax Eckenberg" <deckenberg@dweebsoft.com> To: "Noah Garrett Wallach" <sleek@enabled.com>, "Dan Nelson" <dnelson@allantgroup.com> Cc: <freebsd-questions@FreeBSD.ORG>, "canton" <canton@enabled.com> Subject: Re: iostat - define Kilobits per transfer Message-ID: <0a8401c2c294$22e6e1e0$0a0aa8c0@dweebsoft.com> References: <20030122191542.J76039@typhoon.enabled.com> <20030123032816.GA1799@dan.emsphone.com> <20030122193922.C76039@typhoon.enabled.com>
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> > > I currently have an IDE drive that has the capacity to do 128KB/t and > > > a SCSI drive 64KB/t. Are these stats in fact showing me that there > > > is a limitation with the SCSI drive? Are my file transfering > > > capaibilities less with the SCSI drive? I suppose what do I need to > > > look for in the spcifications when choosing new drives so this does > > > not happen again? > > > > FreeBSD's SCSI layer has a cap of 64k per transaction (apparently > > because ancient ISA adapters could not do more than 64k), and the ATA > > layer has a cap of 128k. You won't see a difference using regular > > disks. A 20MB/sec transfer rate comes out to ~300 64K > > transactions/sec, which most systems should be able to handle with no > > problems. > > > so what exactly does KB per transaction mean? what happens if I am > handling 300 concurrent users with 160Kbit encoded audio streams - could I > in fact do this on this machine? or will I be limited by the 64KB/t > issue? > 300 x 160Kbit = approx. 46Mbit/sec. A new-ish SCSI drive should be able to easily pump out in excess of 200 Mbit/sec. Your bottleneck will be your ethernet adapter long before your local storage. Unless your app is designed very poorly. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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