Re: ATA 4 KiB sector issues.

From: jdow
Date: Wed Mar 17 2010 - 04:11:26 EST


From: "Tejun Heo" <tj@xxxxxxxxxx>
Sent: Tuesday, 2010/March/16 20:44


Hello,

On 03/17/2010 11:51 AM, Kevin Easton wrote:
Can't we fix the problem by defaulting to aligning partitions to
start on an LBA that is a multiple of 64260 ?

Such partitions will always be 4KiB-aligned, *and* start-of-cylinder
aligned (assuming 255/63, as seems to be the norm).

Sure, that reduces your partition granularity to almost-32-MiB, but
that's pretty small potatoes these days (and it's only a *default*, so
you could always override that if you really cared, and didn't need the compatibility).

The only thing we can gain by that is possible compatibility w/ very
old operating systems (<=w2k, BTW, it would be great if someone can
actually test it). Plus, breaking the first cylinder assumption might
not be always safe to begin with. I personally don't think it's
something worth departing from the behavior most vendors would assume
from now on (1MiB alignment). It should be enough and safer to
provide a mechanism to choose legacy alignment if someone is trying to
put something which is older than a decade there.

Thanks.

--
tejun

WRT very old filesystems - it won't affect Amiga partition tables or
the Amiga FFS. It already understands large block sizes natively. And
that's MY definition of "old" with "very" in front of it.

{^_^} Joanne Dow
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