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Date:      Sat, 21 Jan 2012 21:57:52 +0200
From:      Daniel Kalchev <daniel@digsys.bg>
To:        Willem Jan Withagen <wjw@digiware.nl>
Cc:        Alexander Leidinger <Alexander@Leidinger.net>, fs@freebsd.org
Subject:   Re: Question about  ZFS with log and cache on SSD with GPT
Message-ID:  <AD03CC71-8142-4C2B-9FF5-F548EF377464@digsys.bg>
In-Reply-To: <4F1B0177.8080909@digiware.nl>
References:  <4F193D90.9020703@digiware.nl> <20120121162906.0000518c@unknown> <4F1B0177.8080909@digiware.nl>

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

> On 21-1-2012 16:29, Alexander Leidinger wrote:
>>>=20
>=20
>> See
>> =
http://www.leidinger.net/blog/2011/05/03/another-root-on-zfs-howto-optimiz=
ed-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.
>=20
> 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.=20

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=



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