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Date:      Thu, 08 Mar 2012 13:10:38 +0100
From:      "Davide D'Amico" <davide.damico@contactlab.com>
To:        freebsd-fs@freebsd.org
Subject:   Re: freebsd-fs Digest, Vol 455, Issue 4
Message-ID:  <op.waupf0lydwq0iw@davepro.local>
In-Reply-To: <20120308120032.C9FF11065672@hub.freebsd.org>
References:  <20120308120032.C9FF11065672@hub.freebsd.org>

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In data 08 marzo 2012 alle ore 13:00:32, <freebsd-fs-request@freebsd.org>  
ha scritto:

> ------------------------------
> Message: 7
> Date: Thu, 8 Mar 2012 11:35:48 GMT
> From: Martin Simmons <martin@lispworks.com>
> Subject: Re: FreeBSD 9 and gmirror /geom raid
> To: freebsd-fs@freebsd.org
> Message-ID: <201203081135.q28BZmVJ027236@higson.cam.lispworks.com>
>
>>>>>> On Thu, 08 Mar 2012 05:58:11 +0100, Davide D'Amico said:
>>
>> Il 08/03/12 00:02, Freddie Cash ha scritto:
>> > On Wed, Mar 7, 2012 at 6:14 AM, Davide D'Amico
>> > <davide.damico@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.
> I think the problem with the old procedure is that it mirrors the whole  
> disk.
> This fails because both gmirror and GPT store data in the last few  
> blocks of
> the disk.
> If you create gmirror(s) at the GPT partition level instead, then it  
> should be
> safe.

Yes, indeed but I would continue to mirror the entire disk, rather than  
single partitions.

d.



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