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

Pawel Jakub Dawidek pjd at
Mon Dec 6 19:53:39 UTC 2010

On Mon, Dec 06, 2010 at 08:35:36PM +0100, Ivan Voras wrote:
> Please persuade me on technical grounds why ashift, a property
> intended for address alignment, should not be set in this way. If your
> answer is "I don't know but you are still wrong because I say so" I
> will respect it and back it out but only until I/we discuss the
> question with upstream ZFS developers.

No. You persuade me why changing ashift in ZFS, which, as the comment
clearly states is "device's minimum transfer size" is better and not
hackish than presenting the disk with properly configured sector size.
This can not only affect disks that still use 512 bytes sectors, but
doesn't fix the problem at all. It just works around the problem in ZFS
when configured on top of raw disks.

What about other file systems? What about other GEOM classes? GELI is
great example here, as people use ZFS on top of GELI alot. GELI
integrity verification works in a way that not reporting disk sector
size properly will have huge negative performance impact. ZFS' ashift
won't change that.

So you should back this change out, provide technical arguments (if they
exist) that this is the right solution to the problem and not "hey, here
is a patch, I think it is ok".

BTW. ZFS is no longer open-source if you didn't notice.

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