Slow resilvering with mirrored ZIL

[Warren Block]

On Tue, 16 Jul 2013, Gezeala M. Bacuño II wrote:

> On Fri, Jul 5, 2013 at 6:08 PM, Freddie Cash <fjwcash at gmail.com> wrote:
>
>>
>> ZFS- on-Linux has added this as "-o ashift=" property for zpool create.
>>
>> There's a threat on the illumos list about standardising this s across all
>> ZFS- using OSes.
>>
>>
>>
> +1 on this. We tested zfs-on-linux last year and it does automatically
> handle disk partitioning for correct alignment. What we do is just add
> ashift=12 option during zpool create. No more gpart/gnop/ashift/import
> steps.
>
> http://zfsonlinux.org/faq.html#HowDoesZFSonLinuxHandlesAdvacedFormatDrives
>
>
> Back to FreeBSD ZFS,
>
> After reading the thread, I'm still at a loss on this (too much info I
> guess).. regarding gpart/gnop/ashift tweaks for alignment, do we still need
> to perform gpart on newly purchased (SSD/SATA/SAS) Advanced Format drives?
> Or, skip gpart and proceed with gnop/ashift only?

If ZFS goes on a bare drive, it will be aligned by default.  If ZFS is 
going in a partition, yes, align that partition to 4K boundaries or 
larger multiples of 4K, like 1M.

The gnop/ashift workaround is just to get ZFS to use the right block 
size.  So if you don't take care to get partition alignment right, you 
might end up using the right block size but misaligned.

And yes, it will be nice to be able to just explicitly tell ZFS the 
block size to use.