[OpenIndiana-discuss] moving existing rpool onto larger disks, in-place: zpool/zfs ashift/blocksize musings

[Bryan Iotti]

To obtain the ashift value for a pool, try

# zdb <NAME OF POOL> | grep ashift

I've had a terrible experience with my 2TB WD Caviar Green, only recently
improved by separating it from the mirror I had and using it as a long term
backup unit after formatting with a modified version of zpool, called
zpool-12, which sets the proper ashift value.

I think you could get around this issue to use the disk for a normal pool,
where the whole disk is formatted using EFI, but rpool does not use this
setup and instead creates a Solaris partition containing the filesystem. I
hope I am wrong inthis, since 4k drives are becoming more common and can
apparently be a real b### to work with if you want some performance out of
them.

All of this to better support Windows XP (rolleyes)

Bryan
On May 14, 2012 9:01 AM, "Hans J. Albertsson" <
hans.j.albertsson at branneriet.se> wrote:

> I have an OI151a4 system with old 500GB disks in a mirrored pair for the
> rpool, and no further disks.
> For various reasons I'd like to expand the available space by replacing
> the 500GB disks with 2TB disks.
> I'd like to do this IN-PLACE, but I see a few problems in that the new
> disks are naturally 4K blocksize, but falsely report 512 byte blocksize.
>
> First: Can you ever efficiently migrate a zpool with ashift=9 to a 4k
> block disk by just adding the new disk as a 3rd mirror? Regardless of what
> blocksize the disk reports?
>
> Second: Can you manage the problem of the false blocksize report in a
> situation like this?
>
> Third: How can one check to see  what parameters (like ashift( a
> particular pool uses?
>
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