From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Price Date: Thu, 06 Jun 2013 16:17:51 +0100 Subject: [Cluster-devel] [PATCH 2/4] mkfs.gfs2: Align resource groups to RAID stripes In-Reply-To: <1370524289.2744.23.camel@menhir> References: <1370520213-29676-1-git-send-email-anprice@redhat.com> <1370520213-29676-2-git-send-email-anprice@redhat.com> <83456593.48037538.1370523424334.JavaMail.root@redhat.com> <1370524289.2744.23.camel@menhir> Message-ID: <51B0A81F.2010605@redhat.com> List-Id: To: cluster-devel.redhat.com MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit On 06/06/13 14:11, Steven Whitehouse wrote: > It has never been valid to assume that all the rgrps are the same size. > It may be useful as a hint, but we should not be relying on that being > true. Obviously it makes sense to try and keep them to an even spacing > where possible but we must allow for them to be placed and sized > independently as required for alignment, etc. > > There are some restrictions on rgrp length as they need to be aligned > such as to give an integer number of bitmap bytes, and in fact it would > be good if that could be further enforced to ensure that all rgrp > bitmaps are an integer number of 64 bit words in length (so a multiple > of 32 blocks, excluding the headers). So depending on the various > restrictions, there may be a few unused blocks between rgrps in some > cases. This is on my to-do list and should be a case of changing the "& ~(uint32_t)3" parts of rgblocks2bitblocks() but I wanted to make sure that won't break fsck for older file systems first. > It would be worth abstracting the details about alignment from mkfs in > due course, so that fsck also has access to the same information about > where rgrps are likely to have been put, I think. Yes, I need to move the new rgrp creation bits from mkfs into libgfs2 now so that's going to mean updating the other tools to use them eventually (hold onto your hats!). > Some further thoughts: > > - Would it be useful to introduce a flag to show the source of an rgrp > (whether mkfs or gfs2_grow) ? > - Would it be useful to add a creation date stamp to each rgrp so that > we can see when things have happened in the past? Both sound good to me. Andy