Date: Sun, 10 Mar 2013 13:34:48 -0600 (MDT) From: Warren Block <wblock@wonkity.com> To: Cody Ritts <cr@caltel.com> Cc: freebsd-fs@freebsd.org Subject: Re: Aligning MBR for ZFS boot help Message-ID: <alpine.BSF.2.00.1303101326530.7218@wonkity.com> In-Reply-To: <513CD9AB.5080903@caltel.com> References: <513C1629.50501@caltel.com> <alpine.BSF.2.00.1303101006490.5989@wonkity.com> <513CD9AB.5080903@caltel.com>
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On Sun, 10 Mar 2013, Cody Ritts wrote:
> So, aligning to 63MB was still tricky. I found your thread, but I could not
> find step by step how to calculate the offset.
Here is the procedure I had in mind:
# gpart create -s mbr da0
da0 created
root@lightning# gpart add -t freebsd -b 2016 da0
da0s1 added
# gpart show da0
=> 63 39070017 da0 MBR (18G)
63 1953 - free - (976k)
2016 39068064 1 freebsd (18G)
# gpart create -s bsd da0s1
da0s1 created
# gpart add -t freebsd-zfs -a 1m da0s1
da0s1a added
root@lightning# gpart show da0s1
=> 0 39068064 da0s1 BSD (18G)
0 32 - free - (16k)
32 39067648 1 freebsd-zfs (18G)
39067680 384 - free - (192k)
The first slice starts at the last CHS-aligned block before 1M, or 2016.
Misaligned, but not a problem because nothing will be reading from that
location.
The freebsd-zfs partition is created, letting gpart align it to 1M.
gpart starts the partition at an offset of 32, making it the 1M-aligned
block 2048 of the disk.
gpart should also be able to install the bootcode correctly, but I have
not tried it for MBR and ZFS.
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