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Date: Thu, 10 Oct 2013 20:37:54 -0600 (MDT)
From: Warren Block <wblock@wonkity.com>
To: aurfalien <aurfalien@gmail.com>
Subject: Re: 4K vs 512byte sector drives on Seagate Constellation E.2
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On Thu, 10 Oct 2013, aurfalien wrote:

> Hi,
>
> I've a Seagate constellation ES.2 which supports 4K sectors but diskinfo shows it as 512bytes;
>
> da0	512	3000592982016	5860533168	0	0	364801	255	63
>
> I understand that Seagate ships these drives to be compatible with 512byte sectors so that older Windows OSs work on the.
>
> But I'm unsure how to get this drive to report as having 4K sectors.

It does not need to report that, as long as the partitions are aligned 
to 4K blocks.  Seagate has some auto-alignment tech that seems 
reasonably effective.  I'd still make sure the partitions are aligned.

> I'm really asking from a ZFS perspective as my vdevs show with an ashift of 9 via the zdb command.
>
> I'd rather forgo the gnop hack as I prefer a cleaner approach.

Using gnop is the way to force ZFS to use 4K blocks at present.  And 
this does not guarantee alignment with 4K disk blocks, which must be 
accomplished with partition alignment.