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Date:      Sat, 6 Jul 2013 08:10:29 +0300
From:      Daniel Kalchev <daniel@digsys.bg>
To:        Jeremy Chadwick <jdc@koitsu.org>
Cc:        "freebsd-fs@freebsd.org" <freebsd-fs@freebsd.org>
Subject:   Re: Slow resilvering with mirrored ZIL
Message-ID:  <209EBC4A-45C6-4F94-87C3-9679B8A0691E@digsys.bg>
In-Reply-To: <20130705145332.GA5449@icarus.home.lan>
References:  <CBCA1716-A3EC-4E3B-AE0A-3C8028F6AACF@alumni.chalmers.se> <20130704000405.GA75529@icarus.home.lan> <C8C696C0-2963-4868-8BB8-6987B47C3460@alumni.chalmers.se> <20130704171637.GA94539@icarus.home.lan> <2A261BEA-4452-4F6A-8EFB-90A54D79CBB9@alumni.chalmers.se> <20130704191203.GA95642@icarus.home.lan> <43015E9015084CA6BAC6978F39D22E8B@multiplay.co.uk> <CAOjFWZ4obK1cSmvTpW%2Bt4xKdMf%2BkJV5w-sujDT1AZoepj%2B5YrA@mail.gmail.com> <3CFB4564D8EB4A6A9BCE2AFCC5B6E400@multiplay.co.uk> <51D6A206.2020303@digsys.bg> <20130705145332.GA5449@icarus.home.lan>

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On 05.07.2013, at 17:53, Jeremy Chadwick <jdc@koitsu.org> wrote:

> On Fri, Jul 05, 2013 at 01:37:58PM +0300, Daniel Kalchev wrote:
>>=20
>> On 05.07.13 02:28, Steven Hartland wrote:
>>>=20
>>>=20
>>> If anyone wants my current patches which add switch to 4k ashift
>>> by default
>>> as a sysctl + works with QUIRKS too, just let me know.
>>>=20
>>> They are well tested, just we want more options before putting in
>>> the tree.
>>=20
>> Is it not easier to add this as an option to zpool create, instead
>> of an sysctl?
>>=20
>> That is, I believe we have two scenarios here:
>>=20
>> 1. Having an sysctl that instructs ZFS to look at the FreeBSD quirks
>> to decide what the ashift should be, instead of only querying the
>> 'sectorsize' property of the storage. I believe we might not even
>> need an sysctl here, just make it default to obey the quirks --- but
>> sysctl for the interim period will not hurt (with the proper
>> default).
>=20
> I can expand on this one (specifically "relying on sectorsize of the
> media"): no, this will not work reliably, for two reasons. =20

This is how ZFS works now. While I  am we'll aware that most people use disk=
s with all the quirks manufacturers put there, lets not forget ZFS was desig=
ned for the enterprise environment, where "storage device" has much wider me=
aning and "sector size" also varies wildly.

Having said this and because FreeBSD actually goes via geom for disks now, f=
iguring out the correct "sector size" is for geom to do. As it is now, perha=
ps ZFS should be made to query the "stripe size" property of the geom provid=
er and not the "sector size". A sysctl to that effect makes more sense to me=
, will make things more automatic for most users.

Daniel=



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