FreeBSD 9 and gmirror /geom raid

[Freddie Cash]

On Wed, Mar 7, 2012 at 8:58 PM, Davide D'Amico
<davide.damico at contactlab.com> wrote:
> Il 08/03/12 00:02, Freddie Cash ha scritto:
>>
>> On Wed, Mar 7, 2012 at 6:14 AM, Davide D'Amico
>> <davide.damico at contactlab.com>  wrote:
>>>
>>> Hi, I have a server DELL R210 with two sata drives:
>>> ada0 at ahcich0 bus 0 scbus0 target 0 lun 0
>>> ada0:<SAMSUNG HE253GJ 1AJ30001>  ATA-8 SATA 2.x device
>>> ada0: 300.000MB/s transfers (SATA 2.x, UDMA6, PIO 8192bytes)
>>> ada0: Command Queueing enabled
>>> ada0: 238418MB (488281250 512 byte sectors: 16H 63S/T 16383C)
>>> ada0: Previously was known as ad4
>>> ada1 at ahcich1 bus 0 scbus1 target 0 lun 0
>>> ada1:<SAMSUNG HE253GJ 1AJ30001>  ATA-8 SATA 2.x device
>>> ada1: 300.000MB/s transfers (SATA 2.x, UDMA6, PIO 8192bytes)
>>> ada1: Command Queueing enabled
>>> ada1: 238418MB (488281250 512 byte sectors: 16H 63S/T 16383C)
>>> ada1: Previously was known as ad6
>>>
>>> Previously (8.x) - when I didn't use a hw raid - I used to install
>>> freebsd
>>> in a drive (i.e. ad4), boot from it and then:
>>>
>>> # sysctl kern.geom.debugflags=16
>>> # gmirror label -v -b round-robin data ad4
>>> # gmirror insert data ad6
>>> // Modification to /etc/fstab
>>> // reboot
>>>
>>> How could accomplish to the same task with 9.0-RELEASE?
>>
>> http://people.freebsd.org/~rse/mirror/
>>
> Hi Freddie, and thanks for your link.
>
> I followed that procedure until 9.0-RELEASE but the new installer uses GPT
> as the default partition schema, which seems incompatible with gmirror.
>
> I noticed in the handbook
> (http://www.freebsd.org/doc/handbook/geom-mirror.html):
> "The following procedure is also incompatible with the default installation
> settings of FreeBSD 9./X/which use the newGPTpartition scheme. GEOM will
> overwriteGPTmetadata, causing data loss and possibly an unbootable system."
>
> So I think that the old procedure is no more useful.

There's nothing preventing you from using MBR partitioning with BSD
labels, just like in previous releases.  Especially since you only
have 250 GB harddrives (GPT is only required for disks over 2 TB).

If your primary goal is to have mirrored disks, then your best setup
is to gmirror the disks, MBR partition the gm0 device, then BSD label
the slices.

There's nothing carved in stone anywhere that requires you to take the
defaults as gospel.  :)

-- 
Freddie Cash
fjwcash at gmail.com