From: Andi Kleen Subject: Re: Mentor for a GSoC application wanted (Online ext2/3 filesystem checker) Date: Mon, 21 Apr 2008 01:30:08 +0200 Message-ID: <87iqyc85q7.fsf@basil.nowhere.org> References: <20080419012952.GE25797@mit.edu> <20080419185603.GA30449@mit.edu> <480A42F6.2030005@redhat.com> <20080419220432.GB30449@mit.edu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Eric Sandeen , Alexey Zaytsev , linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org, Rik van Riel To: Theodore Tso Return-path: Received: from smtp-out04.alice-dsl.net ([88.44.63.6]:40542 "EHLO smtp-out04.alice-dsl.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750738AbYDTXaZ (ORCPT ); Sun, 20 Apr 2008 19:30:25 -0400 In-Reply-To: <20080419220432.GB30449@mit.edu> (Theodore Tso's message of "Sat, 19 Apr 2008 18:04:32 -0400") Sender: linux-ext4-owner@vger.kernel.org List-ID: Theodore Tso writes: > That would be great, although I think the major issue is not > necessarily the performance problems of using an LVM snapshot on a > very busy filesystem (althouh I could imagine for some users this > might be an issue), but rather for filesystem devices that aren't > using LVM at all. (I've heard some complaints that LVM imposes a > performance penalty even if you aren't using a snapshot; has anyone It always disables barriers if you don't apply a so far unmerged patch that enables them in some special circumstances (only single backing device) Not having barriers sometimes makes your workloads faster (and less safe) and in other cases slower. -Andi