9.1 and gmirror with GPT?
Warren Block
wblock at wonkity.com
Mon Oct 22 22:54:27 UTC 2012
On Mon, 22 Oct 2012, freebsd at johnea.net wrote:
> On 10/21/2012 07:32 AM, Warren Block wrote:
>> On Sun, 21 Oct 2012, Lucas B. Cohen wrote:
>>
>>> On 2012.10.20 20:17, freebsd at johnea.net wrote:
>>>> Just wondering if 9.1 will bring any improvement to the situation of
>>>> creating a full disk geom mirror while also using GPT partition table?
>>>
>>> I'm curious about what this is about. Could you refer me to an article
>>> or a discussion where this issue is described ?
>>
>> The GPT backup partition tables goes at the end of a disk, the same
>> place gmirror(8) and other GEOM modules keep metadata. If GPT
>> partitions are created inside a mirror, the backup GPT table is no
>> longer at the end of the disk. Hiroki Sato created a patch which fixed
>> the gptboot complaints, but there was concern about the nonstandard
>> location of the backup table.
>>
>> At present, MBR partitioning is recommended with gmirror(8).
>
> I've been reading your article on formatting disks in FreeBSD:
> http://www.wonkity.com/~wblock/docs/html/disksetup.html
>
> It's a great description of using gpart to create GPT partitions, and using
> fdisk and bsdlabel to create MBR partitions.
Thanks!
> Would you still recommend this method, using fdisk and bsdlabel, for MRB
> setup?
For drives with 512-byte blocks, they are equivalent. Only gpart can
align the bsdlabel partitions to 4K.
> Do you have any docs on setting up MBR using gpart, to allign for 4K sector
> size drives?
This is a copy from the update of the gmirror section I'm planning to
commit to the Handbook. For a single drive, replace mirror/gm0 with
just the drive name, like ada4.
# create the MBR and add a FreeBSD slice
gpart create -s MBR mirror/gm0
gpart add -t freebsd -a 4k mirror/gm0
# create the bsdlabel partitions in slice 1 (s1)
gpart create -s BSD mirror/gm0s1
gpart add -t freebsd-ufs -a 4k -s 2g mirror/gm0s1
gpart add -t freebsd-swap -a 4k -s 4g mirror/gm0s1
gpart add -t freebsd-ufs -a 4k -s 2g mirror/gm0s1
gpart add -t freebsd-ufs -a 4k -s 1g mirror/gm0s1
gpart add -t freebsd-ufs -a 4k mirror/gm0s1
# put bootcode on the MBR and mark the first slice active
gpart bootcode -b /boot/mbr mirror/gm0
gpart set -a active -i 1 mirror/gm0
# put bootcode on the bsdlabel
gpart bootcode -b /boot/boot mirror/gm0s1
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