On Thu, Jul 28, 2011 at 12:17 AM, Harsh J <ha...@cloudera.com> wrote: > Mohit, > > I believe Tom's book (Hadoop: The Definitive Guide) covers this > precisely well. Perhaps others too. > > Replication is a best-effort sort of thing. If 2 nodes are all that is > available, then two replicas are written and one is left to the > replica monitor service to replicate later as possible (leading to an > underreplicated write for the moment). The scenario (with default > configs) would only fail if you have 0 DataNodes 'available' to write > to.
Thanks Harsh. I think you answered my question. I thought that replication of 3 is a must. And for that you really need atleast 4 nodes so that if one of the nodes die it can still write to 3 nodes. I am assuming writes to replica nodes are always synchronous and not eventually consistent. > > Or are you asking about what happens when a DN fails during a write operation? I am assuming there will be some errors in this case. > > On Thu, Jul 28, 2011 at 5:08 AM, Mohit Anchlia <mohitanch...@gmail.com> wrote: >> Just trying to understand what happens if there are 3 nodes with >> replication set to 3 and one node fails. Does it fail the writes too? >> >> If there is a link that I can look at will be great. I tried searching >> but didn't see any definitive answer. >> >> Thanks, >> Mohit >> > > > > -- > Harsh J >
