[Pc_Support] Re: WD raptor question

[Bryan J. Smith]

On Wed, 2005-08-31 at 17:21 -0400, Ugo Bellavance wrote:
> Hi Bryan (Ugo, on the CentOS list),
> I know you know hardware very well, so I thought I should ask you that
> question.  Feel free to let me know if you don't have time to answer.
> Someone told me recently that the WD raptor HDD are more CPU-hungry
> than other drives, even with a 3ware card.

Integrated Drive Electronics (IDE) talks directly with the chipset via
the AT Attachment (ATA) protocol.  So if there are IDE commands and
setup that is burdening the CPU, it would occur.  It depends on the IDE
approach, the data transfer rate (DTR), seek times, etc...

And yes, there documented cases of CPU load differences between drives,
etc...

But it is _ludicrous_ to suggest the same is true with a 3Ware card.  In
the case of a 3Ware card, _all_ system interaction is handled by its
ASIC, including queuing, transfers, etc...

Same deal with SCSI or SAS.  The SCSI-2 protocol is a standard drive-
host command set and transfer approach, with the host adapter chipset
handling all system-to-bus operations.  No drive to chipset interaction.

So, in a nutshell, I don't think this gentleman knows the first thing
about what he is talking about.

> That person told me he found that info in reviews, but I can't find that.
> Can you confirm that?

And 10,000rpm or even 15,000rpm drives are _definitely_ going to be able
to service _more_ seeks, reads and writes than a 5,400rpm or 7,200rpm
drive.  So what this gentleman is probably referring to is the ability
of 10,000+rpm drives being able to service _more_ requests, which means
there might be more involvement of the CPU which is sending/receiving
more requests.

In a nutshell, it's the side effect of the performance of the drive, and
not a negative.

-- 
Bryan J. Smith     b.j.smith at ieee.org     http://thebs413.blogspot.com
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