From mboxrd@z Thu Jan 1 00:00:00 1970 From: Daniel Phillips Date: Thu, 04 May 2006 20:05:16 -0700 Subject: [Ocfs2-devel] OCFS2 features RFC - separate journal? In-Reply-To: <20060504223037.GB21588@ca-server1.us.oracle.com> References: <20060425183553.GB10524@ca-server1.us.oracle.com> <445936FE.90401@google.com> <44594AE2.9080802@oracle.com> <44594EC9.3040407@google.com> <445A6A61.2090009@oracle.com> <445A7EF3.2000701@google.com> <20060504223037.GB21588@ca-server1.us.oracle.com> Message-ID: <445AC0EC.2000601@google.com> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: ocfs2-devel@oss.oracle.com Mark Fasheh wrote: > Out of curiousity, are we talking about a single journal device (all slot > journals on one disk) or one device per journal? Hi Mark, For me, all journals on one disk, but that is just what I want for my one particular project. The user should be able to specify slot by slot which device the journal is on, if it is not on the main volume. This is just the logical extension of the Ext3 scheme. I don't see that there is anything to be gained by requiring the user to specify a different device for each journal since the user tools already have to handle the case where all the journals are on the same device. The configuration I am most interested at the moment has two nodes, each of which exports one NVRAM disk and one normal disk to the other. The NVRAM disks form a mirror with two journals on it. The normal disks likewise form a mirror with the OCFS2 fs proper on it. The latter volume needs to be snapshotted and its mirror needs a dirty map. The dirty map will live on the (NVRAM) journal volume. See how big a deal it is to be able to factor out the journals like that? As I mentioned earlier, the journals don't need to be snapshotted and the mirror doesn't need a dirty map, which is a really big help considering that typical write latency is determined by the journal, and the latency of a snapshoted, mirrored device with a persistent dirty map can get really high. A picture: Node0 <---- GigE cable ----> Node1 NVRAM: Slot0 Journal Mirror of Slot0 Journal Slot1 Journal Mirror of Slot1 Journal HDISK Dirty Map Mirror of HDISK Dirty Map HDISK: OCFS2 FS proper Mirror of OCFS2 FS proper OCFS2 FS Snapshot Store Mirror of OCFS2 FS Snapshot Store As a side note, separate journals will allow the user to be much less conservative about setting the number of slots. Regards, Daniel