From: Jitesh Shah Subject: Reproducible block structure Date: Mon, 9 Dec 2013 21:03:23 -0800 Message-ID: Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 To: linux-ext4@vger.kernel.org Return-path: Received: from mail-ob0-f175.google.com ([209.85.214.175]:64690 "EHLO mail-ob0-f175.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750737Ab3LJFDX (ORCPT ); Tue, 10 Dec 2013 00:03:23 -0500 Received: by mail-ob0-f175.google.com with SMTP id uz6so4805052obc.34 for ; Mon, 09 Dec 2013 21:03:23 -0800 (PST) Sender: linux-ext4-owner@vger.kernel.org List-ID: Hello all, Assuming I have the latest ext4 system, I have a question -> Scenario -> I have 5 HDDs on which I burn the same block image on. These HDDs are usually mounted RO when used in production. For upgrading, I connect each one to an isolated machine, mount it as RW and run a script to update files (basically add, delete, modify files). Now, if the script is ran in the SAME way for all 5 HDDs, is it guaranteed that these HDDs will be same at the block level too? (i.e. block allocation/deallocation will follow the same pattern). Assume single-core system with only one process modifying the HDD in predetermined order. If there is no way to provide such a guarantee in a default ext4 install, is there an ext4 option (ordered?) which can provide this guarantee? Why do I ask -> I am tinkering with the idea of block level verification of images. If the above guarantees can be provided, I can easily hash the raw HDD for verification purposes. Thanks, Jitesh PS: I am not subscribed to the mailing list, so please include my id in the response if your email client does not put it there already!