Hi,
I have read that snapshots are basicaly symlinks and they do not take that much space. Why if I run nodetool clearsnapshot it frees a lot of space? I am seeing GBs freed...
both together makes sense. Creating a snaphot just creates links for all files unter the snapshot directory. This is very fast and takes no space. But those links are hard links, not symbolic ones.
After a while your running cluster will compact some of its sstables and writing it to a new one as deleting the old ones. Now for example you had SSTable1..4 and a snapshot with the links to those four after compaction you will have one active SSTable5 which is newly written and consumes space. The snapshot-linked ones are still there, still consuming their space. Only when this snapshot is cleared you get your disk space back.
HTH, Jan
