Partitioning questions

Richard Lightman richard at nezumi.plus.com
Sun Oct 6 05:18:47 PDT 2002


* Ben <benhoskings at hotmail.com> [2002-10-06 13:09]:
> dagmar at speakeasy.net wrote:
> >On Fri, 4 Oct 2002, Richard Lightman wrote:
> >
> >
> >>I am a bit suprised by the buffer-cache reads. AFAIK, the bus speed
> >>is 66MHz, and the bus is 16 bits, so how can I get results over
> >>133 MB/sec? The controller is AMD-756 [Viper] IDE (rev 3).
> >
> >
> >Obnoxiously enough, that test merely test whether your CPU is fast enough
> >to recieve the data by copying the same junk data from the buffer over and
> >over--meaning it doesn't send anything across the bus at all.  On anything
> >above a 486 it's a pretty useless do-nothing test now.
> >
> 
> I want to believe you're wrong, and that I do have a special deluxe PCI 
> bus capable of 350 MB/s :D
> 
> /dev/hda:
>  Timing buffer-cache reads:   128 MB in  0.36 seconds =355.56 MB/sec
>  Timing buffered disk reads:  64 MB in  2.68 seconds = 23.88 MB/sec
> 
> /dev/hdc:
>  Timing buffer-cache reads:   128 MB in  0.38 seconds =336.84 MB/sec
>  Timing buffered disk reads:  64 MB in  2.88 seconds = 22.22 MB/sec
> 
> Both the drives are 60GB Maxtor Vipers [7200RPM] FYI.
> 
I did a quick web search and found maxtor vipers are 133MHz ATA drives.
If these are scsi drives, then I might belive values up to 32MB/sec,
but for ATA 133, no matter how fast you PCI bus goes, you are still
limited to 266MB/sec by the IDE bus. If you have some really flashy
IDE controller with built in cache, then you could get these values
from that cache, but however you look at it, 336.84 MB/sec cannot
be measuring the drive cache for an IDE drive.


Richard
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