When to SHARD in SOLR?

Question

From reading on Sharding in SOLR, it is being said that - when an index becomes too large to fit on a single system, an index can be split into multiple shards. How much is too large ? How much amount of indexed data is too large to consider sharding in SOLR?

Answer 1

To me, too large means one or combination of the following:

• does not fit onto the disk (hint: having in mind excess capacity for optimization)
• does not fit into the RAM
• searches are too slow , even after warming it up