Building a case for solr

Question

Our product consists of multiple applications, All using Lucene. 2 of the applications I am involved with have Lucene indexes of about 3 GB and 12GB. Another team is building an application, for which they estimate the LUCENE INDEX size to be close to 1 Terabyte. New documents are added to the indexes every 15 days approx. We do not have any apparent performance issues with the current applications. So my question is

SHould we be using Solr now?

When should one stop using Lucene and graduate to Solr?

Any disadvantages/problems for using Solr?

The client applications are made in ASP.Net, but I assume they will be able to use a solr server using solrnet

Answer 1

I don't think moving from Lucene to Solr is in itself a "graduation". You should just use whatever works best for your particular application, at the same time taking into account the expertise of the dev team.

Moving to Solr does have the advantage of being easily distributed, shall you need it. OTOH if you can fit the 1TB index in a single machine without performance issues, then you don't need to distribute. I don't recommend distributing unless you have to. Distribution means you'll have to maintain N Solr servers instead of just one, so the operational upkeep goes up. Programatically (in the .Net app) there shouldn't be much difference.

Solr is kind of a batteries-included, stand-alone Lucene, implementing features like faceting, caching, spell checking... then again, if you don't need these features and your team is already proficient with Lucene(.net) then stick to Lucene.

Answer 2

Solr wraps your Lucene index with a REST-like interface. You have everything needed to add to, query and administer your index with HTTP methods. So if you need to access your Lucene index on the web, using Solr is the natural way to go.

Maybe a disadvantage I could see is that a Lucene index is usually completely embedded within your application, while a Solr instance will run on a separate process. It could add complexity to your app if you don't need what Solr has to offer.