: Problem solved. We gave the index space five times its original size, just : to be safe. Then the optimize finished without problems and without : leaving deleted, yet still open files behind. During the optimize the : index directory peaked at almost three times its size, and now, : afterwards, it's shrunk by about a fourth!
FWIW: adjusting your mergeFactor so that Solr merges segments more often during regular adds can help reduce the amount of disk needed during a full optimise. Also: the recently added "maxSegments" option on optimize commands can be used to only partially optimize ... i believe a series of partial optimizes might wind up requring less total disk since it gradually frees up disk space merging away the smaller files and lets that space be reclaimed as new searchers get opend and the old searchers close. ... but i haven't really sat down to work it out to make sure i'm correct with that one. -Hoss
