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Date:      Mon, 2 Dec 2013 18:46:42 +0100
From:      Polytropon <freebsd@edvax.de>
To:        "Mike." <the.lists@mgm51.com>
Cc:        freebsd-questions@freebsd.org
Subject:   Re: gmirror, gpart and MBR vs GPT in the Handbook
Message-ID:  <20131202184642.d35c4548.freebsd@edvax.de>
In-Reply-To: <201312021235030914.007AF1DF@smtp.24cl.home>
References:  <201311301303210813.05DE187E@smtp.24cl.home> <alpine.BSF.2.00.1311301352140.99113@wonkity.com> <201312011121580096.005D00FB@smtp.24cl.home> <alpine.BSF.2.00.1312011016490.5791@wonkity.com> <201312021213320528.00673D5F@smtp.24cl.home> <20131202182623.43331984.freebsd@edvax.de> <201312021235030914.007AF1DF@smtp.24cl.home>

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On Mon, 02 Dec 2013 12:35:03 -0500, Mike. wrote:
> On 12/2/2013 at 6:26 PM Polytropon wrote:
> 
> |On Mon, 02 Dec 2013 12:13:32 -0500, Mike. wrote:
> |> My understanding is that MBR can be used with drives only up
> to
> |> and including 2TB in size.  So if I use MBR, the maximum
> drive
> |> size I could use would be 2TB.  Is that correct?
> |[...]
> |Regarding UFS's 2 TB limitation:
> |
> |http://www.freebsd.org/projects/bigdisk/
> |
> |Additionally, MBR can be troublesome on bigger hard disks
> |or stripes.
> |
> |http://www.freebsd.org/doc/handbook/bsdinstall-partitioning.html
> 
> |
> |Today's consensus seems to be:
> |
> |If you use ZFS, let ZFS deal with everything.
> |
> |If you use UFS, use gpart for preparation work. Use GPT when
> |possible, MBR only in exceptions, and dedicated if and only
> |if you really _really_ know what you're doing. :-)
>  =============
> 
> 
> Following the bsdinstall-partitioning link you cited, and then
> following a link on that page, I wind up here:
> 
> http://en.wikipedia.org/wiki/Master_boot_record
> 
> which states:
> 
> "...The organization of the partition table in the MBR limits
> the maximum addressable storage space of a disk to 2 TB ...."
> 
> 
> That (and other places) is where I got the 2TB limit of MBR into
> my head.  Am I misunderstanding that statement?

I think you're correct regarding this finding: The data type 2^32
(because of 32 bit) defines the 2 TB limit. It applies both on
MBR (which stores 32 bit values) and UFS (which also stores 32
bit values). However, I've never dealt with disks > 2 TB _and_
UFS before, so I can't add specific individual findings. :-)

Again, consensus seems to be: If you have big disks, use ZFS.
You use ZFS because the big disks are built into or attached
to big computers with sufficient RAM, so it won't be a problem.



-- 
Polytropon
Magdeburg, Germany
Happy FreeBSD user since 4.0
Andra moi ennepe, Mousa, ...



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