Date: Fri, 5 Jul 2013 16:52:26 +0100 From: "Steven Hartland" <killing@multiplay.co.uk> To: "Jeremy Chadwick" <jdc@koitsu.org>, "Daniel Kalchev" <daniel@digsys.bg> Cc: freebsd-fs@freebsd.org Subject: Re: Slow resilvering with mirrored ZIL Message-ID: <D1AA0DF1F1954FFF9A99759A93B1BAEA@multiplay.co.uk> 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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----- Original Message -----
From: "Jeremy Chadwick" <jdc@koitsu.org>
> I'm not "damning FreeBSD", I'm just stating that this is the reality of
> the situation. For example -- only recently in stable/9 (maybe
> stable/8, didn't look) were quirks added for Intel SSDs which came to
> market over 2 years ago (BTW thanks for adding those Steve).
Just to confirm both stable/8 and stable/9 are in sync with head for all
the SSD quirks.
> Even if there was a way to rectify that scenario in an efficient manner
> (the quirks right now are hard-coded in kernel space), it wouldn't
> change this scenario:
I've thought about that too, it would be really nice not to have to recompile
to add a QUIRK. I also know scottl has some ideas on how to improve CAM which
may well enable us to config these things much easier.
>> 2. Have an option to zpool create and zpool add, that specifies the
>> ashift value. Here my thinking is that it should let you specify an
>> ashift equal or larger than the computed one, which is based on the
>> largest sector size of all devices in a vdev.
>
> I'm very much a supporter of the option being added to one of the ZFS
> commands. I'm not against Steve's sysctl, but the problem with that is
> more of a social one: features like this (if committed) never end up
> being announced to the world in a useful manner, so nobody knows they
> exist until it's too late. It would also just make me wonder "why
> bother with the sysctl at all, just use 4096 universally going forward,
> and have whatever code/bits still support cases where existing setups
> use 512" (last part sounds easier than probably done, not sure).
The primary reason for not having it hard coded is while its good for
99% of use cases there's still that extra 1%. Which is why I think
from a FreeBSD perspective having the option to configure the default,
but still having the standard as 4k is where my mind is.
> As for the "basing things on sector size" -- see my above explanation
> for why/how this isn't entirely reliable. Manufacturers, argh! :-)
>
> But something like "zpool create -a 12 ..." would be a blessing, because
> I'd just use that all the time. If changing the default from 9 to 12
> isn't plausible, then at least offering what I just described would be a
> good/worthwhile stepping stone.
Indeed.
Regards
Steve
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