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Date: Tue, 29 Jan 2013 14:01:13 -0700 (MST)
From: Warren Block <wblock@wonkity.com>
To: Artem Kuchin <matrix@itlegion.ru>
Subject: Re: Software raid VS hardware raid
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On Tue, 29 Jan 2013, Artem Kuchin wrote:

>
> 29.01.2013 18:57, Warren Block:
>> On Tue, 29 Jan 2013, Artem Kuchin wrote:
>> 
>> The Handbook chapter on gmirror talks about the problems with GPT and GEOM 
>> metadata.  In short: right now, they conflict.  It's possible to mirror GPT 
>> partitions, but be aware that if you mirror more than one partition on a 
>> drive, a rebuild after replacing a drive could thrash the heads as mirrors 
>> are rebuilt simultaneously.
>> 
>> http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/geom-mirror.html 
>> 
>> 
>
> So,
> gmirror+GPT=conflict on last sector
> GPT+gmirror = hardrive head kill
>
> nice...
>
> So, for no more than 2TB disks the best way to go is GMIRROR of the drive 
> +PARTITION on top of it?

GPT partitions should work, just limit it to one mirrored partition per 
drive.

> Or maybe there is a way to instruct gmirror do rebuild only what i say 
> (manual rebuild) ?

'gmirror configure -n' ?  Have not tried it.  The trick would be to do 
that before multiple mirrors start rebuilding, which they will as soon 
as geom_mirror.ko is loaded.