One segment is in-use, being searched. That segment (and others) are merged into a new segment. After the new segment is ready, searches are directed to the new copy and the old copies are deleted.
That is how two copies are needed. If you cannot provide 2X the disk space, you will not have a stable Solr installation. You should consider a different search engine. “Optimizing” (forced merges) will not help. It will probably cause failures more often because it always merges the larges segment. Walter Underwood wun...@wunderwood.org http://observer.wunderwood.org/ (my blog) On May 4, 2015, at 3:53 AM, Rishi Easwaran <rishi.easwa...@aol.com> wrote: > Thanks for the responses Mark and Ramkumar. > > The question I had was, why does Solr need 2 copies at any given time, > leading to 2x disk space usage. > Not sure if this information is not published anywhere, and makes HW > estimation almost impossible for large scale deployment. Even if the copies > are temporary, this becomes really expensive, especially when using SSD in > production, when the complex size is over 400TB indexes, running 1000's of > solr cloud shards. > > If a solr follower has decided that it needs to do replication from leader > and capture full copy snapshot. Why can't it delete the old information and > replicate from scratch, not requiring more disk space. > Is the concern data loss (a case when both leader and follower lose data)?. > > Thanks, > Rishi. > > > > > > > > -----Original Message----- > From: Mark Miller <markrmil...@gmail.com> > To: solr-user <solr-user@lucene.apache.org> > Sent: Tue, Apr 28, 2015 10:52 am > Subject: Re: Multiple index.timestamp directories using up disk space > > > If copies of the index are not eventually cleaned up, I'd fill a JIRA > to > address the issue. Those directories should be removed over time. At > times > there will have to be a couple around at the same time and others may > take > a while to clean up. > > - Mark > > On Tue, Apr 28, 2015 at 3:27 AM Ramkumar > R. Aiyengar < > andyetitmo...@gmail.com> wrote: > >> SolrCloud does need up to > twice the amount of disk space as your usual >> index size during replication. > Amongst other things, this ensures you have >> a full copy of the index at any > point. There's no way around this, I would >> suggest you provision the > additional disk space needed. >> On 20 Apr 2015 23:21, "Rishi Easwaran" > <rishi.easwa...@aol.com> wrote: >> >>> Hi All, >>> >>> We are seeing this > problem with solr 4.6 and solr 4.10.3. >>> For some reason, solr cloud tries to > recover and creates a new index >>> directory - (ex:index.20150420181214550), > while keeping the older index >> as >>> is. This creates an issues where the > disk space fills up and the shard >>> never ends up recovering. >>> Usually > this requires a manual intervention of bouncing the instance and >>> wiping > the disk clean to allow for a clean recovery. >>> >>> Any ideas on how to > prevent solr from creating multiple copies of index >>> directory. >>> >>> > Thanks, >>> Rishi. >>> >> > >
