Hubert Verstraete wrote:
Bill Davidsen wrote:
Luca Berra wrote:
On Tue, Mar 25, 2008 at 05:57:06PM +0100, Hubert Verstraete wrote:
Neil Brown wrote:
On Thursday March 13, hubskml@xxxxxxx wrote:
Neil,
What is the status of the major for the partitionable arrays ?
automatically determined at runtime.
I see that it is 254, which is in the experimental section,
according to the official Linux device list
(http://www.lanana.org/docs/device-list/).
Will there be an official registration ?
No. Is there any need?
I got this question in mind when I saw that mkfs.xfs source code
was referring to the MD major to tune its parameters on an MD
device, while it ignores MDP devices.
If there were reasons to register MD, wouldn't they apply to MDP too ?
i don't think so:
bluca@percy ~ $ grep mdp /proc/devices
253 mdp
Why is it important to have XFS tune its parameters for md and not
for mdp? I don't understand your conclusion here, is tuning not
needed for mdp, or so meaningless that it doesn't matter, or that XFS
code reads /proc/devices, or ??? I note that device-mapper also has a
dynamic major, what does XFS make of that?
It reads from /proc/devices.
I don't know how much difference tuning makes, but if it's worth
doing at all, it should be done for mdp as well, I would think.
Same thought. I wrote the patch for mkfs.xfs but did not publish it
for two reasons:
1) MD is registered but not MDP. Now I understand, it's not a problem,
we just need to read /proc/devices as device-mapper does.
2) Tuning XFS for MDP can be achieved through the mkfs.xfs options.
With a few lines in shell, my XFS on MDP now has the same performance
as XFS on MD.
Hopefully the following patch will be picked up by vendors. Now from the
linux-kernel list there have been two recent changes in similar areas,
the ability of loop to support partitionable devices, and the ability to
have nbd handle partitionable devices. Are XFS users so lucky that this
change would also improve things for those media?
--
Bill Davidsen <davidsen@xxxxxxx>
"Woe unto the statesman who makes war without a reason that will still
be valid when the war is over..." Otto von Bismark
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