From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from 220-245-31-42.static.tpgi.com.au ([220.245.31.42]:43577 "EHLO smtp.sws.net.au" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751420AbaEOJAP convert rfc822-to-8bit (ORCPT ); Thu, 15 May 2014 05:00:15 -0400 Received: from xev.localnet (localhost [127.0.0.1]) by smtp.sws.net.au (Postfix) with ESMTP id F0B9020941 for ; Thu, 15 May 2014 19:00:11 +1000 (EST) From: Russell Coker To: linux-btrfs Reply-To: russell@coker.com.au Subject: staggered stripes Date: Thu, 15 May 2014 19:00:10 +1000 Message-ID: <2751140.Zb1qMBeNgk@xev> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Sender: linux-btrfs-owner@vger.kernel.org List-ID: http://www.cs.wisc.edu/adsl/Publications/corruption-fast08.html Page 13 of the above paper says: # Figure 12 presents for each block number, the number of disk drives of disk # model ‘E-1’ that developed a checksum mismatch at that block number. We see # in the figure that many disks develop corruption for a specific set of block # numbers. We also verified that (i) other disk models did not develop # multiple check-sum mismatches for the same set of block numbers (ii) the # disks that developed mismatches at the same block numbers belong to # different storage systems, and (iii) our software stack has no specific data # structure that is placed at the block numbers of interest. # # These observations indicate that hardware or firmware bugs that affect # specific sets of block numbers might exist. Therefore, RAID system designers # may be well-advised to use staggered stripes such that the blocks that form # a stripe (providing the required redundancy) are placed at different block # numbers on different disks. Does the BTRFS RAID functionality do such staggered stripes? If not could it be added? I guess there's nothing stopping a sysadmin from allocating an unused partition at the start of each disk and use a different size for each disk. But I think it would be best to do this inside the filesystem. Also this is another reason for having DUP+RAID-1. -- My Main Blog http://etbe.coker.com.au/ My Documents Blog http://doc.coker.com.au/