Date: Wed, 12 Nov 2003 14:54:12 -0800
From: "Randy.Dunlap" <rddunlap@osdl.org>
To: Peter Chubb <peter@chubb.wattle.id.au>
Cc: mfedyk@matchmail.com, info@avistor.com, linux-kernel@vger.kernel.org
Subject: Re: 2 TB partition support
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On Tue, 11 Nov 2003 14:42:30 +1100 Peter Chubb <peter@chubb.wattle.id.au> wrote:

| >>>>> "Mike" == Mike Fedyk <mfedyk@matchmail.com> writes:
| 
| > On Mon, Nov 10, 2003 at 06:12:06PM -0800, Joseph Shamash wrote:
| >> 
| >> What is the maximum partition size for a patched 2.4.x kernel, and
| >> where are those patches?
| 
| Mike> I believe it is now 16TB per block device in 2.6, and patched
| Mike> 2.4.
| 
| That's right for 32-bit systems with 4k pages.  For 64 bit systems the
| limit is over 8 Exabytes.
| 
| You should note that software raid has smaller limits, as does the
| LVM.  Also the 2.4 patches have seen *much* less testing than the 2.6
| mainline (except possibly on the SGI Altix).
| 
| What exactly are you trying to do?


I made the table below for LinuxWorld Expo/Conference in Aug. 2002,
for Linux 2.4.x on 32-bit architectures, so it is a bit out of date,
but it might be helpful or useful.

--
~Randy
MOTD:  Always include version info.


Linux 2.4 filesystem limits on 32-bit architectures,
with 4 KB block sizes:


                     ext2/3fs    reiserfs     JFS       XFS#
max filesize:          4 TB&      16 TB$     16 TB$%  16 TB$
max filesystem size:  16 TB&      16 TB&     16 TB$   16 TB$
		                              4 PB&    8 EB&
kernel bldev limit:    2 TB        2 TB       2 TB     2 TB 


Notes:
#: all kernel limits
$: kernel limit
%: 4 KB pages
@: block device limit: 2 TB (or 1 TB if signed)
&: fs limit


Another look at ext2/3fs limits:

  Assumes using 4 KB block sizes on a 32-bit architecture
  (64-bit architecture isn't very limiting).

Largest limiting factor
           |
	   v
Smallest limiting factor


1.  64-bit API limit:  8 EiB

2.  kernel page cache index limit (32 bits) == filesystem block number:
    2^32 * 4 KB = 16 TiB

3.  ext2fs triple-indirect block limit:  4 TiB

4.  kernel block device limit (device sector number):  2 TiB
    (or 1 TiB if signed)

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