We have a big JIRA instance on a really good hardware:
- ~300k issues
- 48GB RAM
- 32 cores
- SSD in RAID
- PostgreSQL on localhsot
Still, reindexing does not increase the load above 4-5 (out of 32!), database is not under high load nor the filesystem.
Clearly this means that indexing is not properly using the resources in order to index rapidly.
Even with this configuration, a foreground reindex takes about one hour which is too much for a live system, in fact is too much even for a background reindex.
By default, Jira uses 10 Reindexing threads. You can tune number of jira index threads.