Subject: Re: comparing raid-like filesystems
To: Manuel Bouyer <>
From: Chuck Silvers <>
List: current-users
Date: 02/02/2003 12:26:11
On Sun, Feb 02, 2003 at 09:12:24PM +0100, Manuel Bouyer wrote:
> On Sun, Feb 02, 2003 at 09:06:10AM -0800, Jason R Thorpe wrote:
> > On Sun, Feb 02, 2003 at 01:31:25PM +0000, Martin J. Laubach wrote:
> > 
> >  >   (b) no MAXPHYS at all and let the low level driver deal with
> >  >       segmenting large requests if necessary
> > 
> > This is clearly what we prefer.
> If we go this way, we'll probably have to do it at an upper level,
> to avoid code duplication if various drivers.
> Do you see anything wrong with making MAXPHYS per-device ?

the question here is, what layer should know how to do i/o breakup?
currently file systems and other callers have to do it, and having
a per-device MAXPHYS wouldn't change that.  since this is really a
device (or possibly bus) limitation, it seems better to do it below
the file system.  you're saying you don't want each disk driver to have
custom code for this, and that would also be good.  so this is really
the job of some middle layer between the file system and the disk driver.
there are other things that should probably go in such an intermediate
layer as well, such as partitioning.