On 08/17/16 10:56, Andriy Gapon wrote:
On 17/08/2016 19:36, Nathan Whitehorn wrote:
OK, so then what is the solution here? We have a number of tools that need to
know this information: gpart, sade, bsdinstall, zfs, graid, etc. If we want to
have a consistent set of defaults -- for example, to use 4K across the board,
which I think is a good idea -- there should be a central place to set this that
does not involve hacking a variety of independent tools. Do you disagree?
I don't care how that happens. It happens that the way we currently encode this
is geom stripesize. If we feel like we can't get this right in drivers, then we
should provide a tunable to set a minimum default alignment. You could implement
this in lots of different ways. But having static values hardcoded in random
places that makes similar tools (sade, gpart) behave inconsistently cannot
possibly be the answer.
This is my point, from beginning to end. Is there any reason -- at all -- that
we should prefer per-tool one-off changes to fixing the central mechanism we
already have to give consistent results that we think are reliable?
It would be perfect to get a correct description of a disk and to do that in
central place. But still I, as a user / administrator, want to be able to
_force_ the alignment that I want when I partition a disk, create a filesystem,
etc. That is, even if the kernel reports the perfectly correct information and
the tools know how to automatically do what's best for me, I still want to eb
able to override. And I think that installers and administrative tools should
provide a way to do that. And many already do, e.g. 'gpart add -a X'.
So, I do not see how striving for the better disk detection (in a central place)
and having more knobs in the administration tools are mutually exclusive or
conflicting goals.
Just my two bits.
Agreed 100%. The issue here is that this kind of patch unconditionally
overrides the kernel in an unsettable way. I think the right scheme is:
1. Try to get the real values as much as possible.
2. Provide a global hint to all tools that you want some value (e.g. 4K)
unless the drivers are *sure* it's the wrong answer.
3. Have options in individual tools to force other values.
We have (1), though it can probably be improved, and (3) and just need (2).
-Nathan
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