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Re: 2 Terabyte File System Size Limitation

To: "Davida, Joe" <Joe_Davida@xxxxxxxxxx>
Subject: Re: 2 Terabyte File System Size Limitation
From: "Andi Kleen" <ak@xxxxxxx>
Date: Fri, 1 Sep 2000 14:19:36 +0200
Cc: "'linux-xfs@xxxxxxxxxxx'" <linux-xfs@xxxxxxxxxxx>
In-reply-to: <09D1E9BD9C30D311919200A0C9DD5C2C02536F84@xxxxxxxxxxxxxxxxxxxxxxx>; from Joe_Davida@xxxxxxxxxx on Thu, Aug 31, 2000 at 03:44:34PM -0600
References: <09D1E9BD9C30D311919200A0C9DD5C2C02536F84@xxxxxxxxxxxxxxxxxxxxxxx>
Sender: owner-linux-xfs@xxxxxxxxxxx
On Thu, Aug 31, 2000 at 03:44:34PM -0600, Davida, Joe wrote:
>       Is there any information on the 2 TBytes file system
>       limitation in Linux which is also inherited by the
>       linux port of xfs? What imposes this limitation?
>       Are the current efforts aimed at removing this
>       limitation? I hear ReiserFS has a 16 Terabyte
>       file system size.

The 2TB limitation is caused by the interface between block drivers
and file systems. On 32bit machines a 32bit value is used to pass the
sector number, with the sector being in 512byte units. Limiting yourself
to 31bits is probably safer to protect against signedness bugs in the
driver.

That gives you a 2^31 * 2^9 = 2^40bits block device size limit for all
file systems and raw devices.

On 64bit systems the limit is higher, assuming there are no 32bit limitations
in the driver.


-Andi

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