Theodore Tso wrote:
On Thu, Dec 11, 2008 at 07:24:31PM -0500, Ric Wheeler wrote:
More than a year back, I was the sacrificial Linux person invited to
represent Linux at IDEMA. At that point, I seem to remember that Vista
supported native 4k drives only on data partitions (non-boot) and that
they required a 1MB alignment (no more odd 512 byte sector offsets).
I can talk to the folks to confirm, but my understanding is that they
are resigned to random unaligned 4k writes because Windows does this.
When I told them that we tried very hard to do write coalescing and
filesystems could be made to understand to align things on RAID stripe
boundaries, they seemed surprised (because Windows doesn't do this).
So as far as I know 4k alignment is all they need. And this is
something very simple we can do, either in distribution installers
forcibly sending a configuration parameter to the partition editors,
or changing the partition editors to have better defaults, or changing
the kernel to report different fantasy geometries if we can't find a
valid MBR partition label.
Also, they seem to be talking about 2011 for the 4k sector rollout,
which means Windows 7....
The disk manufacturers basically know that they will get tons
(literally!) of returned disks if they don't emulate 512 byte support -
boot loaders, old BIOS's, etc all will generate these accesses.
It would be nice to get a mode bit that allowed you to test pure 4k
drives to help us insure that we do the right thing despite this.
The trick is to actually get your hands on these parts, I think that
they are starting to trickle out.
ric
I don't think that this is a hard problem to fix, just get someone to
give us drives and we can work through the details (grub, etc)...
I don't think it's a hard problem either. My thinking though was that
if we start making changes now, then we can avoid the rush for the
enterprise distro's 2 years from now. :-) And the changes really seem
to be quite trivial, and low risk; simply making the partitions to be
appropriately aligned and then running in Windows compatibility mode
should be quite simple.
- Ted
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