From mboxrd@z Thu Jan 1 00:00:00 1970 From: Theodore Ts'o Subject: Re: Does ext4 write anything during reading with relatime? Date: Mon, 7 Dec 2015 18:19:13 -0500 Message-ID: <20151207231913.GA3094@thunk.org> References: <5662C472.2050902@inbox.ru> <20151206211454.GB2614@thunk.org> <5665FD3D.1050603@inbox.ru> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: linux-ext4@vger.kernel.org To: The Ghost Return-path: Received: from imap.thunk.org ([74.207.234.97]:44215 "EHLO imap.thunk.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932555AbbLGXTP (ORCPT ); Mon, 7 Dec 2015 18:19:15 -0500 Content-Disposition: inline In-Reply-To: <5665FD3D.1050603@inbox.ru> Sender: linux-ext4-owner@vger.kernel.org List-ID: On Tue, Dec 08, 2015 at 12:42:21AM +0300, The Ghost wrote: > > I just tried again. With relatime or noatime, the second drive spins up. > Always. With read-only, it never spins up. And that doesn't make sense... The superblock *does* get modified at mount time to update the last mount time and the mount count in the superblock. But I've tested using blktrace, and that's the only write I see after copying in a set of test files, reading them (so that atime > mtime), and then umounting the file system. I then started the blktrace, mounted the file system, and read all of the files using "tar cvzf /tmp/foo.tar.gz /mnt". Cheers, - Ted