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Date:      Thu, 16 Aug 2018 16:32:52 -0700
From:      Freddie Cash <fjwcash@gmail.com>
To:        Steven Hartland <killing@multiplay.co.uk>
Cc:        FreeBSD Stable <freebsd-stable@freebsd.org>
Subject:   Re: zfs boot size
Message-ID:  <CAOjFWZ4k%2B1rqXd%2B7PwXJsb%2BYvdwGDqXmkxjsO8t7bi3jC=7nGg@mail.gmail.com>
In-Reply-To: <469d704c-3635-2da9-39b6-1f25eae384d7@multiplay.co.uk>
References:  <m2wosqothk.wl-randy@psg.com> <469d704c-3635-2da9-39b6-1f25eae384d7@multiplay.co.uk>

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On Thu, Aug 16, 2018, 4:22 PM Steven Hartland, <killing@multiplay.co.uk>
wrote:

> The recommended size for a boot partition has been 512K for a while.
>
> We always put swap directly after it so if a resize is needed its easy
> without and resilvering .
>
> If your pool is made up of partitions which are only 34 block smaller
> than your zfs partition you're likely going to need to dump and restore
> the entire pool as it won't accept vdevs smaller than the original.
>

Adding "-a 1M" to your gpart command when partitioning disks, regardless of
their use, is very handy for this. It starts the first partition at 1MB,
which gives you enough slack to increase the size of the freebsd-boot
partition as needed. :)

You can even add a freebsd-boot partition to make a data pool bootable as
root with that amount of slack. :D Went through that at home.

And ZFS has reserved a few MB from the end of the device you give it to
allow for replacement drives that aren't the exact same size (in sectors or
bytes) for awhile now (maybe since the 9.x days?).

Cheers,
Freddie

Typos courtesy of my phone's keyboard.



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