linux-ext4 - Re: EXT4 Larger Than 16TB

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Message-ID: <20130709021403.GC6000@thunk.org>
Date:	Mon, 8 Jul 2013 22:14:03 -0400
From:	Theodore Ts'o <tytso@....edu>
To:	Michael <mike@...ftx.net>
Cc:	linux-ext4@...r.kernel.org
Subject: Re: EXT4 Larger Than 16TB

On Mon, Jul 08, 2013 at 04:32:50PM -0500, Michael wrote:
> I have a currently 15TB FS that I want to expand to 18TB.
> Unfortunately EXT4 e2fsprogs has an issue that stops you from being
> able to do this:
> 
> sudo resize2fs /dev/md0
> resize2fs 1.42.5 (29-Jul-2012)
> resize2fs: New size too large to be expressed in 32 bits
> 
> It seems to me, reading the change logs, that this only supported if
> you created your FS with 64 bit specified. There seems to have been a
> patch last year that added support for changing 32->64bit, but I had a
> hard time finding/tracking that.

Unfortuantely, there is no patch that would enable this.

In theory it could be done; it would require doubling the size of the
block group descriptors, which would require moving other metadata
blocks out of the way.  Resize2fs does do this when growing a file
system off-line when no blocks are available from the resize inode,
but no one has implemented the necessary changes to extend this to
adding the 64-bit feature.

So it's technically possible, but it's not implemented at this time.

Sorry,

							- Ted
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