Date: Tue, 10 Oct 1995 21:34:43 -0400 (EDT) From: "Jonathan M. Bresler" <jmb@kryten.Atinc.COM> To: Bruce Evans <bde@zeta.org.au> Cc: chuckr@eng.umd.edu, se@ZPR.Uni-Koeln.DE, hackers@FreeBSD.org Subject: Re: VLB Disk Controllers Message-ID: <Pine.3.89.9510102100.S18159-0100000@kryten.atinc.com> In-Reply-To: <199510100147.LAA32670@godzilla.zeta.org.au>
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On Tue, 10 Oct 1995, Bruce Evans wrote:
> Testing /dev/sd0 tests the buffer cache and shouldn't go anywhere near
> the driver or the drive. There may be more variance because running
> the program (not to mention other processes) disturbs the buffer cache.
> /dev/sd0 is about twice as slow as /dev/zero here, but the "command"
> overhead is about twice as small for /dev/sd0.
i get /dev/zero nearly 3x slower than /dev/sd0
144 vs 50
/dev/rsd0 is much slower.
./disklatency /dev/zero
Command overhead is 144 usec (time_4096 = 235, time_8192 = 326)
transfer speed is 4.50987e+07 bytes/sec
Aspen: {232} ^zero^sd0
./disklatency /dev/sd0
Command overhead is 50 usec (time_4096 = 245, time_8192 = 441)
transfer speed is 2.0966e+07 bytes/sec
Aspen: {233} ^sd0^rsd0
./disklatency /dev/rsd0
Command overhead is 1169 usec (time_4096 = 1696, time_8192 = 2222)
transfer speed is 7.78268e+06 bytes/sec
>
> Bruce
>
Jonathan M. Bresler jmb@kryten.atinc.com | Analysis & Technology, Inc.
FreeBSD Postmaster jmb@FreeBSD.Org | 2341 Jeff Davis Hwy
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