Subject: Re: comparing raid-like filesystems
To: None <email@example.com>
From: Thor Lancelot Simon <firstname.lastname@example.org>
Date: 02/02/2003 00:51:39
On Sun, Feb 02, 2003 at 01:04:57PM +1030, Greg 'groggy' Lehey wrote:
> On Saturday, 1 February 2003 at 23:22:13 +0100, Manuel Bouyer wrote:
> > On Sat, Feb 01, 2003 at 07:54:27PM +0100, Pavel Cahyna wrote:
> >>> Right, this is a deficiency in how we handle layered disk I/O. Right
> >>> now we are limited to MAXPHYS (64k) for each "disk". If this "disk"
> >> Why this limit? Is this a heritage from PDP-11 with its (i think) 64kB address
> >> space?
> > Some popular disk standart (IDE comes to mind, there may be others) don't
> > support transfers > 64k.
> No, that's not correct:
Yes, it is correct. Your test doesn't measure what you think it does;
the PCI IDE hardware really, truly can't DMA across a 64K boundary.