[lug] Re: advice on disk configuration

[pjr at ucar.edu]

On Mon, Nov 17, 2003 at 12:04:13PM -0700, Zan Lynx wrote:
> 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.

Thanks for straightening me out. Now my question is, are the numbers I
quote below reasonable for a high performance PCI bus, controller and
ATA/100 disk? They are only 50% of the slowest theoretical transfer
rates you quote above, and much less than the numbers you quote for a
66Mhz PCI bus (which is what I have). I poked around a bit on machines
at work, and the fastest speeds I found on those machines were order
70MB/sec. So my numbers are 20% slower than the fastest rates I came
across. 

Phil

> hdparm -d1 /dev/hde
> hdparm -tT /dev/hde
> 
> /dev/hde:
>  Timing buffer-cache reads:   2624 MB in  2.00 seconds = 1312.00  MB/sec
>  Timing buffered disk reads:  168 MB in  3.00 seconds =  56.00 MB/sec
> 


-- 
Phil Rasch, Climate Modeling Section, National Center for Atmospheric Research
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