Does moving existing Solr instance to SolrCloud require re-indexing?

Question

How do I go about migrating an existing Solr instance (4.2.1) with several cores to SolrCloud (4.6.1)? Will I have to re-index the data?

Answer 1

If re-index is feasible - I would vote for it.

Unless you are specifically interested in DocValues, you don't have to upgrade the index format. See codec history here: https://lucene.apache.org/core/4_6_0/core/org/apache/lucene/codecs/lucene46/package-summary.html Make sure everything is backed up and indexes are in sync among replicas before trying.

Answer 2

unlikely(from 4.2 to 4.6) you need to re-index everything but usually it's a good practice to re-index your data since you will creating newer version of lucene indexes that maximize your chance of a smooth migration.