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To: asami@freebsd.org (Satoshi Asami)
cc: freebsd-scsi@freebsd.org, freebsd-current@freebsd.org,
        freebsd-isp@freebsd.org
Subject: Re: Streamlogic RAID array benchmarks 
In-reply-to: Your message of Fri, 20 Sep 96 18:43:44 -0700.
             <199609210143.SAA13100@silvia.HIP.Berkeley.EDU> 
Date: Fri, 20 Sep 1996 21:11:37 -0700
From: "Michael L. VanLoon -- HeadCandy.com" <michaelv@MindBender.serv.net>
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> * >Just FYI, we've seen close to 30MB/s with ccd (no mirroring).  You
> * >need two 2940?W's (or one 3940?W) and at least four disks though.
> * 
> * Just for our edification, what kind of CPU did you use?
> * 
> * Also For Everyones' Information, you won't get close to that on a real
> * filesystem unless you use a Pentium or better.

>Yeah, it's a P5 (133MHz).  We got pretty much the same result with the
>P6 (200MHz) too (which is kinda surprising, given that their memory
>system is so much slower).

How is that surprising?  The SCSI controller lives on the other side
of the bus, and does the bus-mastering irrespective of the CPU.  The
CPU does not do bcopies for bus-mastering SCSI transfers.

The problems with the 486 is that its slowness causes too great a
latency between when work becomes available, and when it has something
ready to keep the disk subsystem working, causing less than 100%
efficiency.  If all have a (working) PCI bus, what happens on the SCSI
controller side should not be affected by the CPU, except for how busy
the CPU can keep the SCSI controller.

-----------------------------------------------------------------------------
  Michael L. VanLoon                           michaelv@MindBender.serv.net
        --<  Free your mind and your machine -- NetBSD free un*x  >--
    NetBSD working ports: 386+PC, Mac 68k, Amiga, Atari 68k, HP300, Sun3,
        Sun4/4c/4m, DEC MIPS, DEC Alpha, PC532, VAX, MVME68k, arm32...
    NetBSD ports in progress: PICA, others...
-----------------------------------------------------------------------------