From mboxrd@z Thu Jan 1 00:00:00 1970 From: Theodore Ts'o Subject: Re: [PATCH 37/37] ext5: define new subtype to add features and reduce testing complexity Date: Tue, 6 May 2014 11:21:29 -0400 Message-ID: <20140506152129.GA31730@thunk.org> References: <20140501231222.31890.82860.stgit@birch.djwong.org> <20140501231629.31890.34812.stgit@birch.djwong.org> <20140506013317.GO8434@birch.djwong.org> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: "Darrick J. Wong" , linux-ext4@vger.kernel.org To: =?utf-8?B?THVrw6HFoQ==?= Czerner Return-path: Received: from imap.thunk.org ([74.207.234.97]:52251 "EHLO imap.thunk.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757573AbaEFPVd (ORCPT ); Tue, 6 May 2014 11:21:33 -0400 Content-Disposition: inline In-Reply-To: Sender: linux-ext4-owner@vger.kernel.org List-ID: On Tue, May 06, 2014 at 02:50:39PM +0200, Luk=C3=A1=C5=A1 Czerner wrote= : > meta_bg - Just makes group descriptors to be spread across the file > system. It has been around for some time and I am not sure > why this is not a default already. It should also increase > the limit of the file system size but I am not sure whether > this is still true with flex_bg ? meta_bg signiicantly slows down mount operations (and in general, any operation where we need to read in the block group descriptors --- i.e., dumpe2fs, e2fsck, etc.) The strategy for meta_bg is that it's something that we enable as we need it, as part of an online or off-line resize. That way, we keep the block groups contiguous for as long as possible. Once the resize inode has been exhausted (which _will_ happen when the file system size grows beyond 16T), the resize operation will turn off the resize_inode feature and then enable the meta_bg feature. And this is all working today, with the latest kernel and e2fsprogs; so there's no reason to enable meta_bg as part of mke2fs operation, and a good reason not to enable it by default, but to let resize2fs turn it on when it makes sense to do so. - Ted -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" i= n the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html