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Date:      Mon, 02 Jun 2014 08:38:13 -0400
From:      Allan Jude <allanjude@freebsd.org>
To:        freebsd-hackers@freebsd.org
Subject:   Re: fdisk(8) vs gpart(8), and gnop
Message-ID:  <538C7035.5080700@freebsd.org>
In-Reply-To: <538B4FD7.4090000@freebsd.org>
References:  <20140601004242.GA97224@bewilderbeast.blackhelicopters.org> <CAOjFWZ5N9FGwgSz0_YFNQjavzdJDitRn52VKn4ipW1ddj6-weQ@mail.gmail.com> <BCA9F5D6-3925-4E7E-9082-128652508305@FreeBSD.org> <3D6974D83AE9495E890D9F3CA654FA94@multiplay.co.uk> <538B4CEF.2030801@freebsd.org> <1DB2D63312CE439A96B23EAADFA9436E@multiplay.co.uk> <538B4FD7.4090000@freebsd.org>

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On 2014-06-01 12:07, Nathan Whitehorn wrote:
> 
> So the discussion here is related to what to do about the installer. The
> current ZFS component unconditionally creates gnops all over the place
> to set ashift to 4k. That's across the board worse: it has exactly the
> performance impact of changing the default of this sysctl (whatever that
> is), it can't easily be overridden (which the sysctl can), and it's a
> horrible hack to boot. There are a few options:
> 
> 1. Change the default of vfs.zfs.min_auto_ashift
> 2. Have the same effect but in a vastly worse way by adjusting the
> installer to create gnops
> 3. Have ZFS choose by itself and decide to do that permanently.
> 
> Our ATA code is good about reporting block sizes now, so (3) isn't a big
> issue except for the mixed-pool case, which is a huge PITA.
> 
> We need to choose one of these. I favor (1).
> -Nathan
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I favour 1 as well.

Note: the current ZFS installer script forces 4k with gnop if the option
is turned on (it is by default), but you can have it not use gnop.

But yes, this new sysctl (it is very new), is great. Will it be MFC'd in
time for 9.3?

-- 
Allan Jude



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