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Date:      Thu, 23 Jan 2003 08:08:33 +0100
From:      Mark Rowlands <fuc952d@tninet.se>
To:        Noah Garrett Wallach <sleek@enabled.com>
Cc:        freebsd-questions@FreeBSD.ORG
Subject:   Re: iostat - define Kilobits per transfer
Message-ID:  <200301230808.33307.fuc952d@tninet.se>
In-Reply-To: <20030122203914.T76039@typhoon.enabled.com>
References:  <20030122191542.J76039@typhoon.enabled.com> <0a8401c2c294$22e6e1e0$0a0aa8c0@dweebsoft.com> <20030122203914.T76039@typhoon.enabled.com>

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On Thursday 23 January 2003 5:40 am, Noah Garrett Wallach wrote:
> On Wed, 22 Jan 2003, Dax Eckenberg wrote:
> > > 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.
>
> okay things are getting clearer over here.  what exactly does KB
> per transaction mean?  I dont understand what this describes?
>
> - Noah
>
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my guess :- 

iostat -Iw 60 -t da

 ad0
KB/t    Xfrs MB
8.42    71    0.58

so over the period,  71 transfers occurred totalling 0.58MB for an average 
KB/t of (0.58*1024) / /71   = 8.37 KB/t   but maybe the actual avg transfer 
size is recorded and summarized giving that slight variation?.  Try a longer 
period and see, or read the code......   (the math starts around line 
600....) 

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