From: Eric Sandeen Subject: Re: Ext4 Size Restrictions Date: Mon, 09 Jun 2014 13:11:34 -0500 Message-ID: <5395F8D6.6010409@redhat.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit To: Mahesh Khanwalkar , linux-ext4 Return-path: Received: from mx1.redhat.com ([209.132.183.28]:49443 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753764AbaFISLg (ORCPT ); Mon, 9 Jun 2014 14:11:36 -0400 In-Reply-To: Sender: linux-ext4-owner@vger.kernel.org List-ID: On 6/9/14, 1:03 PM, Mahesh Khanwalkar wrote: > Hello, > Ext4 supports max file size of 16TiB and max volume of 1EiB. What > exactly in the implementation causes this restriction? Also is there > any plans (as of now) to make it max sizes larger? The ext4 extent format on disk is: struct ext4_extent { __le32 ee_block; /* first logical block extent covers */ __le16 ee_len; /* number of blocks covered by extent */ __le16 ee_start_hi; /* high 16 bits of physical block */ __le32 ee_start_lo; /* low 32 bits of physical block */ }; The file size is limited by a 32-bit number for the starting logical block of an extent, ee_block. 2^32 * 4k blocks gives 16TiB The 48 bits for physical start high/low gives you the 1 EiB (2^48*4096). I don't know of any plans to make either of these larger. Surely 1EiB suffices for now. 16TiB, perhaps not so much. -Eric > Thanks, > Mahesh Khanwalkar