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Date:      Thu, 24 Jan 2013 22:46:37 +0200
From:      Daniel Kalchev <daniel@digsys.bg>
To:        Borja Marcos <borjam@sarenet.es>
Cc:        FreeBSD Filesystems <freebsd-fs@freebsd.org>, freebsd-scsi@freebsd.org, Steven Hartland <killing@multiplay.co.uk>
Subject:   Re: Problem adding SCSI quirks for a SSD, 4K sector and ZFS
Message-ID:  <92BD25C7-FC6C-41AF-80AE-05AAD4CD4659@digsys.bg>
In-Reply-To: <FF2FCD9E-0CA5-4030-8881-C866FA97CF1D@sarenet.es>
References:  <492280E6-E3EE-4540-92CE-C535C8943CCF@sarenet.es> <A71C9D2FA3984F6A84CED6DE3E21DDCF@multiplay.co.uk> <FF2FCD9E-0CA5-4030-8881-C866FA97CF1D@sarenet.es>

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On Jan 24, 2013, at 6:09 PM, Borja Marcos <borjam@sarenet.es> wrote:

> Oh, sorrry for the confusion! I assumed that the da driver would =
announce a 4 KB sector instead of the 512 bytes due to the quirks.=20
>=20
> Which  brings an interesting question, I might have a potential time =
bomb in my experimental machine at home. It's a ZFS mirror with two 500 =
MB disks. One of the has 512 byte sectors, the other is "advanced =
format".=20


If you did not create your zpool with ashift=3D12, then you have the =
bomb already. Disks with different native sector size coexist quite =
happily in the same zpool. If the storage does not lie, ZFS will in fact =
use the largest 'sector size' and everything will be ok. Many (most) =
advanced format drives however lie about their sector size and pretend =
to have 512 byte sectors. If you create an zpool with such a drive and =
an 'normal' 512 byte drive without explicitly requesting 4k alignment, =
thing are bad.

Daniel=



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