svn commit: r216230 - head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs

Pawel Jakub Dawidek pjd at
Tue Dec 7 11:04:17 UTC 2010

On Tue, Dec 07, 2010 at 12:25:34PM +0200, Alexander Motin wrote:
> It is really nice that we support bigger sector sizes. But unluckily we
> are not the only OS in universe. Disks with data may move between
> systems, partition could be shared, etc. We must keep compatibility --
> period. Can you predict what happen if we try to use some FAT partition
> created by Windows (using 512bytes sectors) after we set disk sector
> size to 4K? I have feeling that we won't even read partition table
> properly, not speaking about FAT. Even GEOM classes supporting big
> sector sizes depend on that size to be constant -- otherwise they will
> just be unable to locate their own metadata in last sector.

First valid argument, thank you:)

BTW. What Ivan did changes ashift for existing ZFS pools as well, so it
breaks them too.

If we decide to align other things to stripesize we can still break
compatibility with other operating systems.
Also stripesize is really not good idea. For RAID5 it might be like
64kB or larger, which is definiately too large for ashift in ZFS or
fragment size in UFS.

Pawel Jakub Dawidek             
pjd at                 
FreeBSD committer                         Am I Evil? Yes, I Am!
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