Well, that blog post is, at best, an estimate based on disk head seek times so take it with a large grain of salt, I probably shouldn't even have put that in the post.....
But for a single node, it's probably not all that noticeable. Erick On Tue, Aug 27, 2013 at 12:20 PM, Sandro Zbinden <zbin...@imagic.ch> wrote: > @Mark Do you know how I can set the syncLevel to fsync in the > solrconfig.xml I can't find in the default solrconfig.xml > > > https://svn.apache.org/repos/asf/lucene/dev/trunk/solr/example/solr/collection1/conf/solrconfig.xml > > The blog posts at > http://searchhub.org/2013/08/23/understanding-transaction-logs-softcommit-and-commit-in-sorlcloud/says > that enabling the fsync is not a big increase in the update time (a > few milliseconds (say 10-50 ms)). So I think It is useful to turn on fsync. > > On Aug 27, 2013, at 11:54 AM, Erick Erickson <erickerick...@gmail.com> > wrote: > > > Soft commits flush to the op system, so a JVM crash/termination > > shouldn't affect it anyway. > > A soft commit is not a hard commit, so there are not guarantees like this. > It searches committed and non committed segments - non committed segments > will not magically be committed after a JVM crash. > > > Turning on the fsync > > would just be a little bit of extra protection.. > > If you don't have replication, it turns on strong 'durability' promises. > Without it, you are on your own if you have a hard machine reset. If > durability is important to you and you don't have replication, it's > important to use the fync option here. Unless you have a great, long time, > battery backup and/or an env such that hard resets don't concern you for > some reason. It comes down to your requirments. > > Responses to Sandro inline below: > > On Aug 27, 2013, at 11:43 AM, Sandro Zbinden <zbin...@imagic.ch> wrote: > > > Hey Mark > > > > Thank you very much for the quick answer. We have a single node > environment. > > > > I try to find the fsync option but was not successful. Ended up in the > > UpdateLog class :-) > > > > How do I enable fsync in the solrconfig.xml ? > > In the updateLog config, its a syncLevel=fsync param. > > > > > > > Besides that: > > > > If solr soft commit feature has a on disk guarantee with a transaction > log why we don't use solr soft commit as the default commit option ? > > Yes, for visibility you should use soft commit. You should also have an > auto hard commit with openSearcher=false - it's just about flushing the > transaction log and freeing memory in this configuraiton - which is why it > makes sense to simply turn on the auto commit for regular hard commits. You > may or may not want to use auto soft commits. > > - Mark > > > > > > > -----Ursprüngliche Nachricht----- > > Von: Mark Miller [mailto:markrmil...@gmail.com] > > Gesendet: Dienstag, 27. August 2013 17:12 > > An: solr-user@lucene.apache.org > > Betreff: Re: Transaction log "on-disk" guarantees > > > > > > On Aug 27, 2013, at 11:08 AM, Sandro Zbinden <zbin...@imagic.ch> wrote: > > > >> Can we activate the transaction log to have on disk guarantees and then > use the solr soft commit feature ? > > > > Yes you can. If you only have a single node (no replication), you > probably want to turn on fsync via the config. > > > > - Mark > > > >
