On Thu, Dec 9, 2010 at 10:40 PM, Bill de hÓra <b...@dehora.net> wrote: > > > On Tue, 2010-12-07 at 21:25 -0500, Edward Capriolo wrote: > > The idea behind "micrandra" is for a 6 disk system run 6 instances of > Cassandra, one per disk. Use the RackAwareSnitch to make sure no > replicas live on the same node. > > The downsides > 1) we would have to manage 6x the instances of cassandra > 2) we would have some overhead for each JVM. > > The upsides ? > 1) Since disk/instance failure only degrades the overall performance > 1/6th (RAID0 you lost the entire node) (RAID5 still takes a hit when > down a disk) > 2) Moves and joins have less work to do > 3) Can scale up a single node by adding a single disk to an existing > system (assuming the ram and cpu is light) > 4) OPP would be "easier" to balance out hot spots (maybe not on this > one in not an OPP) > > What does everyone thing? Does it ever make sense to run this way? > > It might for read heavy loads. > > When I looked at this, it was pointed out to me it's simpler to run fewer > bigger coarser nodes and take the entire node/server out when something goes > wrong. Basically give each Cassandra a server. > > I wonder if it would be better to rethink compaction if that's what's > driving the idea. It seems to what is biting everyone, along with GC. > > Bill
Having 6 IP's on a machine would be a given in this setup. That is not an issue for me. It is not "biting" me. We all know that going from 10-20 nodes is pretty simple. However organic growth from 10-16, then a couple months later from 16 - 22, can take some effort with 300-600 GB per node, since each join and clean up can take a while. I am wondering if dividing a single large node into multiple smaller instances would make this type of growth easier.
