linux-ext4 - Re: Possible ext2 bug with large sparse files?

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Message-ID: <20070605135606.GE12755@thunk.org>
Date:	Tue, 5 Jun 2007 09:56:06 -0400
From:	Theodore Tso <tytso@....edu>
To:	Mark Knibbs <markk@...ra.co.uk>
Cc:	linux-ext4@...r.kernel.org
Subject: Re: Possible ext2 bug with large sparse files?

On Tue, Jun 05, 2007 at 01:25:29PM +0100, Mark Knibbs wrote:
> For whatever reason, it seems the maximum file size for that
> partition is 17,247,252,480 bytes. In itself that behaviour isn't 
> necessarily a bug; but if you have any clue how the ext2 maximum file size 
> is related (or not) to the amount of free space or the volume size, please 
> let me know!

You're using a filesystem with a 1k blocksize, and that's the cause of
the limit.  The maximum number of 1k blocks that can be addressed
using the direct/indirect scheme is:

	12 + 256 + 256*256 + 256*256*256 = 16843020 blocks

or
	16843020 blocks * 1024 bytes/block =  17,247,252,480 bytes

Unless you are using a really tiny filesystem, you really don't want
to be using 1k block sizes; in addition to imposing this 16GB file
size limit, it also makes the filesystem much more inefficient for
large files.

Regards,

						- Ted
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