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Date:      Wed, 22 Jan 2003 19:44:22 -0800 (PST)
From:      Noah Garrett Wallach <sleek@enabled.com>
To:        Dan Nelson <dnelson@allantgroup.com>
Cc:        freebsd-questions@FreeBSD.ORG, canton <canton@enabled.com>
Subject:   Re: iostat - define Kilobits per transfer
Message-ID:  <20030122193922.C76039@typhoon.enabled.com>
In-Reply-To: <20030123032816.GA1799@dan.emsphone.com>
References:  <20030122191542.J76039@typhoon.enabled.com> <20030123032816.GA1799@dan.emsphone.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?

- Noah



>
> --
> 	Dan Nelson
> 	dnelson@allantgroup.com
>

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