[lug] Re: advice on disk configuration

[Zan Lynx]

On Sun, 2003-11-16 at 18:24, Phil Rasch wrote:
[snip]
> I guess I am confused because I am seeing the clock rate reported as
> 66MHz for the controller and disk, and somewhow I expected it to
> correlate with the maximum burst rate for those devices, which are 133
> and 100 respectively.
[snip]
> I used the "lshw" command to query the kernel about
> what hardware it sees. it reports the following for the controller and
> disk.
> 
>           *-storage
>                 description: Unknown mass storage controller
>                 product: 20269
>                 vendor: Promise Technology, Inc.
>                 physical id: 2
>                 bus info: pci at 02:02.0
>                 version: 02
>                 clock: 66MHz
>                 capabilities: bus_master cap_list
>                 configuration: driver=Promise irq=17
>               *-ide:0
>                    description: Channel 0

I believe the clock: 66MHz you see here is the PCI bus speed and has
nothing to do with the disk interface speed.  

Standard PCI is 32-bit, 33 MHz, and can therefore transfer about 133
megabytes per second.  That isn't fast enough for servers and RAID
disks, so there is 32-bit, 66 MHz PCI at 266 megabytes per second and
64-bit, 66 MHz PCI which can transfer about 533 megabytes per second. 
There there's PCI-X which you can get on some server boards and the Mac
G5, which is 64-bit, 133 MHz.

-- 
Zan Lynx <zlynx at acm.org>
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