From: Andreas Dilger Subject: Re: [RFC] store RAID stride in superblock Date: Thu, 24 May 2007 05:44:42 -0600 Message-ID: <20070524114442.GA12526@schatzie.adilger.int> References: <20070512020248.GQ6375@schatzie.adilger.int> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Theodore Ts'o To: linux-ext4@vger.kernel.org Return-path: Received: from mail.clusterfs.com ([206.168.112.78]:52877 "EHLO mail.clusterfs.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755254AbXEXLoo (ORCPT ); Thu, 24 May 2007 07:44:44 -0400 Content-Disposition: inline In-Reply-To: <20070512020248.GQ6375@schatzie.adilger.int> Sender: linux-ext4-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org On May 22, 2007 01:22 +0530, Kalpak Shah wrote: > __u16 s_raid_stride; /* RAID stride */ > - __u16 s_pad; /* Padding */ > + __u16 s_mmp_interval; /* Wait for # seconds in MMP > checking */ > + __u64 s_mmp_block; /* Block for multi-mount protection > */ Ted, I just noticed this updated patch w.r.t. your recent s_raid_stride addition. I also want to have a separate parameter for "s_raid_stripe_width" which is normally N * s_raid_stride, where N is the number of disks in a RAID 5 N+1 (or RAID 6 N+2) parity stripe. This is for delalloc+mballoc to allow it to align and size new allocations so that writes do not impose read-modify-write overhead on the RAID stripes. My understanding from the code is that s_raid_stride is to put the bitmaps for different groups on different disks to avoid always having a single disk busy with bitmap updates. Cheers, Andreas -- Andreas Dilger Principal Software Engineer Cluster File Systems, Inc.