> -----Original Message-----
> From: Alex Turner [mailto:[EMAIL PROTECTED]
> Sent: Monday, April 18, 2005 5:50 PM
> To: Bruce Momjian
> Cc: Kevin Brown; firstname.lastname@example.org
> Subject: Re: [PERFORM] How to improve db performance with $7K?
> Does it really matter at which end of the cable the queueing is done
> (Assuming both ends know as much about drive geometry etc..)?
The parenthetical is an assumption I'd rather not make. If my
performance depends on my kernel knowing how my drive is laid
out, I would always be wondering if a new drive is going to
break any of the kernel's geometry assumptions. Drive geometry
doesn't seem like a kernel's business any more than a kernel
should be able to decode the ccd signal of an optical mouse.
The kernel should queue requests at a level of abstraction that
doesn't depend on intimate knowledge of drive geometry, and the
drive should queue requests on the concrete level where geometry
matters. A drive shouldn't guess whether a process is trying to
read a file sequentially, and a kernel shouldn't guess whether
sector 30 is contiguous with sector 31 or not.
David B. Held
Software Engineer/Array Services Group
200 14th Ave. East, Sartell, MN 56377
320.534.3637 320.253.7800 800.752.8129
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