From mboxrd@z Thu Jan 1 00:00:00 1970 From: Iordan Iordanov Subject: write barriers on raid0 and raid10 Date: Tue, 08 Jun 2010 14:23:04 -0400 Message-ID: <4C0E8A88.8010906@cdf.toronto.edu> References: Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-raid-owner@vger.kernel.org To: linux-raid@vger.kernel.org List-Id: linux-raid.ids Hi, We are designing a rather involved file server with an ext3 formatted stripe (raid0) sitting on top of raid10 devices. Each raid10 device sits on top of 3 iscsi targets, and has layout n3 (so it is effectively a 3 way mirror). We chose raid10 over raid1 due to an apparent read performance benefit of raid10. We are trying to decide whether to upgrade to a kernel newer than 2.6.34, where write barriers are ostensibly supported by all possible raid types, because we are worried about ext3 corruption with no write barrier support. However, we are also worried about whether write barriers really "make sense" in a multi-disk environment and are wondering whether they will actually make a difference in our setup. For argument's sake, let's assume that our drives honor write cache flushes. Can somebody shed some light on how write barriers are implemented in raid0 and raid10? Also, any critical comments on the validity of our setup and/or assumptions is also welcome. Many thanks! Iordan Iordanov