Oh, I just realized that was only a partial solution to the problem. I forgot to commit related logic that handles selecting the same directory on vnode restart. That's what I get for sending out code late at night. You'll want to maintain a partition->directory index somewhere to really make it work (or search all directories for an existing bitcask corresponding to the partition).
For what it's worth, my experiments a few months back in this area just used a deterministic function to map partitions to a directory. That's another approach. -Joe On Tue, Mar 22, 2011 at 1:25 AM, Joseph Blomstedt <joseph.blomst...@gmail.com> wrote: > Each vnode already opens a separate bitcask, therefore there isn't any > necessary factor preventing the desired behavior. It's just not coded > that way. While an individual bitcask must be a single directory, > there is no reason all vnodes need to open bitcasks within a shared > root directory. > > Luckily, it's easy to change this behavior. In fact, I played around > with the idea awhile back. This question prompted me to find/release > the code: > https://github.com/jtuple/riak_kv/commit/a8ab33224651e6850aed385e4c05c1993916a3e5 > > That commit should apply against riak-0.14.1. It extends the bitcask > data_root config option to allow for multiple root paths as well as a > selection strategy (random or spread). Random just randomly chooses > one of the directories. Spread picks the directory containing the > fewest already-opened bitcasks -- although, this is a soft guarantee > since no effort is taken to address multiple vnodes choosing a > directory concurrently. > > Using paths that correspond to different mounted drives should do the trick. > > -Joe > > > On Mon, Mar 21, 2011 at 5:29 PM, Greg Nelson <gro...@dropcam.com> wrote: >> Hello, >> We are currently evaluating Riak for an application that will store large >> amounts of data in a write-heavy pattern. We'd like to pack many disks into >> each machine. Currently, it appears that Bitcask uses exactly one directory >> to store data. What is the best way to have it use multiple disks? Is this >> something Innostore would handle better? >> We'd like to avoid RAID since we'll be paying for redundancy at a higher >> level with Riak (N=3, etc.). >> We'd also like to avoid a JBOD type setup where a single disk failure brings >> the whole node down, as we'll obviously be increasing those odds with each >> disk. >> What I'm wondering is, can each node distribute its vnodes across many >> disks? And if one of those disks fails, will Riak handle that appropriately >> (i.e., the other vnodes continue to operate normally and hand-off data when >> the new disk comes online)? >> Thanks! >> Greg >> _______________________________________________ >> riak-users mailing list >> riak-users@lists.basho.com >> http://lists.basho.com/mailman/listinfo/riak-users_lists.basho.com >> >> > _______________________________________________ riak-users mailing list riak-users@lists.basho.com http://lists.basho.com/mailman/listinfo/riak-users_lists.basho.com
