From: Jitesh Shah Subject: Re: Reproducible block structure Date: Tue, 10 Dec 2013 10:08:04 -0800 Message-ID: References: <20131210134255.GA31214@thunk.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Cc: linux-ext4 To: "Theodore Ts'o" Return-path: Received: from mail-ob0-f179.google.com ([209.85.214.179]:60364 "EHLO mail-ob0-f179.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754683Ab3LJSIG (ORCPT ); Tue, 10 Dec 2013 13:08:06 -0500 Received: by mail-ob0-f179.google.com with SMTP id wm4so5699880obc.38 for ; Tue, 10 Dec 2013 10:08:04 -0800 (PST) In-Reply-To: <20131210134255.GA31214@thunk.org> Sender: linux-ext4-owner@vger.kernel.org List-ID: .. inline .. > > 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. > > Nope, there's no way to guarantee this. Thanks. I was quite sure of this, but still thought it was a good idea to ask in case I am missing an obscure detail. > > 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. > > If you want to do a block level verification of the image, why not > also do block level update of the image as well? Yep. Thats the plan B. We had a bunch of utilities using file-based approaches. I was trying to find a way to move them one-by-one. Looks like moving to a block-based approach altogether is a more worthwhile investment of time. Thanks a lot for your responses Carlos and Ted. Jitesh