Make ZFS use the physical sector size when computing initial ashift

[Steven Hartland]

There's lots more to consider when considering a way foward not least of all
ashift isn't a zpool configuration option is per top level vdev, space
consideration of moving from 512b to 4k, see previous and current discussions
on zfs-devel at freebsd.org and zfs at lists.illumos.org for details.

    Regards
    Steve

----- Original Message ----- 
From: "Borja Marcos" <borjam at sarenet.es>

On Jul 10, 2013, at 11:25 AM, Steven Hartland wrote:

> If others are interested I've attached this as it achieves what we needed here so
> may also be of use for others too.
> 
> There's also a big discussion on illumos about this very subject ATM so I'm
> monitoring that too.
> 
> Hopefully there will be a nice conclusion come from that how people want to
> proceed and we'll be able to get a change in that works for everyone.

Hmm. I wonder if the simplest approach would be the better. I mean, adding a flag to zpool.

At home I have a playground FreeBSD machine with a ZFS zmirror, and, you guessed it, I was
careless when I purchased the components, I asked for two "1 TB drives" and that I got, but different
models, one of them "advanced format" and the other one "classic".

I don't think it's that bad to create a pool on a classic disk using 4 KB blocks, and it's quite likely that
replacement disks will be 4 KB in the near future. 

Also, if you use SSDs the situation is similar.


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