Question about ZFS with log and cache on SSD with GPT

[Daniel Kalchev]

On Jan 21, 2012, at 8:18 PM, Willem Jan Withagen wrote:

> On 21-1-2012 16:29, Alexander Leidinger wrote:
>>> 
> 
>> See
>> http://www.leidinger.net/blog/2011/05/03/another-root-on-zfs-howto-optimized-for-4k-sector-drives/
>> for a description how to align to 4k sectors. I do not know if the main
>> devices of the pool need to be setup with an emulated 4k size (the gnop
>> part in my description) or not, but I would assume all disks in the
>> pool needs to be setup with the temporary gnop setup.
> 
> Well one way of resetting up the harddisks would be to remove them from
> the mirror each in turn. Repartion, and then rebuild the mirror, hoping
> that that would work, since I need some extra space to move the
> partitions up. :(

With ZFS, the 'alignment' is on per-vdev -- therefore you will need to recreate the mirror vdevs again using gnop to make them 4k aligned. 

Only one disk in a vdev needs to be 'gnop-ed' to 4k sectors because ZFS uses the largest sector size from all devices in a vdev as the vdev 'ashift' at creation time.

Daniel