Pros and Cons of amd64 (versus i386).

[Christian Lopez de Castilla Wagner]

On Sun, 2006-04-09 at 13:22 -0500, Matthew D. Fuller wrote:
> On Sat, Apr 08, 2006 at 06:00:56PM -0600 I heard the voice of
> Scott Long, and lo! it spake thus:
> > 
> > Modern disks (I don't know how to define a cutoff to this term,
> > unfortunately) definitely put more bits onto the outer rim of the
> > platter than the inner rim.
> 
> Pretty much any disk you'd currently find, I'd say.
> 
> diskinfo -t won't run through on my 4 or 2 gigs ("disk too small for
> test"  :), but on my 9 gigger:
> 
> Transfer rates:
>         outside:       102400 kbytes in   5.215159 sec =    19635 kbytes/sec
>         middle:        102400 kbytes in   6.268067 sec =    16337 kbytes/sec
>         inside:        102400 kbytes in   8.237962 sec =    12430 kbytes/sec
> 
> da4 at ahc2 bus 0 target 5 lun 0
> da4: <IBM DNES-309170W SAH0> Fixed Direct Access SCSI-3 device 
> da4: 40.000MB/s transfers (20.000MHz, offset 31, 16bit), Tagged Queueing Enabled
> da4: 8748MB (17916240 512 byte sectors: 255H 63S/T 1115C)
> 
> 


Just for comparison:
root at hellion# diskinfo -t ad1
ad1
        512             # sectorsize
        61492838400     # mediasize in bytes (57G)
        120103200       # mediasize in sectors
        119150          # Cylinders according to firmware.
        16              # Heads according to firmware.
        63              # Sectors according to firmware.

Seek times:
        Full stroke:      250 iter in   5.650173 sec =   22.601 msec
        Half stroke:      250 iter in   4.581880 sec =   18.328 msec
        Quarter stroke:   500 iter in   7.510191 sec =   15.020 msec
        Short forward:    400 iter in   3.556557 sec =    8.891 msec
        Short backward:   400 iter in   3.294277 sec =    8.236 msec
        Seq outer:       2048 iter in   0.285684 sec =    0.139 msec
        Seq inner:       2048 iter in   0.288960 sec =    0.141 msec
Transfer rates:
        outside:       102400 kbytes in   1.896157 sec =    54004
kbytes/sec
        middle:        102400 kbytes in   2.297042 sec =    44579
kbytes/sec
        inside:        102400 kbytes in   3.853005 sec =    26577
kbytes/sec

ad1: 58644MB <IC35L060AVV207 0 V22OA63A> at ata0-slave UDMA100

As you can see, the outside is more than twice as fast in this case.
Just a guess, since both are IBM disks: You're using a
Workstation/Server disk, which probably performs in a more balanced way
across the platter, while this (consumer disk) is not
performance-oriented. Maybe SCSI and IDE devices are not as similar as
we all thought?

-- 

Christian Lopez de Castilla Wagner
lopisaur at gmail.com
lopisaur at acelerate.com
(+591-705)98290
http://lopisaur.googlepages.com
http://lopisaur.blogspot.com
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