On Fri, Apr 10, 2015 at 4:00 PM, Roman Tkachenko <ro...@mailgunhq.com> wrote:
> * Can I just move some SSTables data files from "sstables2" to "sstables1" > which has much more free disk space? Will Cassandra start fine after that > and not lose any data? > Cassandra generally discovers files in its data directories and treats them as legitimate files. I do not have specific knowledge of JBOD behavior here, but I would presume it would be the same. > * Provided multiple data dirs, should Cassandra distribute data equally > between them? In what I'm observing this is almost always not true. On that > particular node I mentioned above the difference is huge: 4% occupied disk > space for "sstables1" and 87% for "sstables2"; on other nodes the situation > is a little better but still not 50/50. > No, and especially not when using Size Tiered Compaction. I honestly wonder why people think JBOD is a useful feature for Cassandra. You don't really want to continue to operate a node that has lost half of its data, and managing multiple data directories seems relatively likely to be more trouble than it's worth. You have a distributed, replicated database... just replace nodes when they fail. Anyone care to set me straight about the amazing benefits they see which make the costs worthwhile? =Rob
