(An earlier post seems not to have gone through. My apologies in the eventual case of a duplicate.)
I'm thinking of using Riak to replace a large Oracle system, and I'm trying to understand its guarantees. I have a few introductory questions; this is the first of three. I'm trying to understand the reliability of stored data. Imagine (for example) that I have 5 Riak hosts, and an n_val of 3. Imagine that each host is down 1% of the time (I bought the disks at a flood sale), and imagine that host failures are uncorrelated, and imagine that when hosts come back up, they stay up long enough to fully rejoin the service, and imagine that I haven't done any writes for a long while. Given these assumptions, I might naïvely assume that my data are available with a probability of about 99.999%, or down about 5 minutes a year. This would be great (perhaps). Of course, this ignores the possibility that some of my data may not be replicated at all, perhaps even with all three copies on the same host. If all I know is that some data may not be replicated, then all I know is that (some of) my data may be unavailable as much as 3.65 days a year, which would not be nearly as great. I understand things probably won't be this bad, but "probably" isn't a probability. Is this right? Is there anything I can do to guarantee higher reliability, short of setting n_val to 5? Cheers, John _______________________________________________ riak-users mailing list riak-users@lists.basho.com http://lists.basho.com/mailman/listinfo/riak-users_lists.basho.com
