From mboxrd@z Thu Jan 1 00:00:00 1970 From: Daniel Phillips Date: Wed, 03 May 2006 17:46:01 -0700 Subject: [Ocfs2-devel] OCFS2 features RFC - separate journal? In-Reply-To: <44594AE2.9080802@oracle.com> References: <20060425183553.GB10524@ca-server1.us.oracle.com> <445936FE.90401@google.com> <44594AE2.9080802@oracle.com> Message-ID: <44594EC9.3040407@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 Zach Brown wrote: > Daniel Phillips wrote: >>Sorry about the lag. Here's an easy feature nobody has mentioned so far, and >>from my reading isn't supported: separate journal, like Ext3. > > Yeah, I think this would be a fine piece to have some day. Ext3 has it today. > I'm not sure it's a high priority, though, given that the vast majority > of deployments are already using hardware that has either some form of > write caching or so many spindles that external journals just aren't > worth the time they take to configure. The journal has different, less demanding mirroring requirements than the filesystem proper. It is unnecessary and redundant to have a dirty map for the journal mirror. It is also unnecessary and stupid to snapshot the journal. These two things add up to a _huge_ performance boost for the journal, if it can be separated. It is worth remembering that not every OCFS2 user will be running it on a big expensive SAN. Probably not even the majority. > I'd be interested in seeing more careful write ordering in JBD before > worrying about external journals, personally. IMHO, the separate journal on NVRAM will yield a much bigger gain and be much less work besides. Agreed that improvements to JBD are good. They are also scary. Regards, Daniel