Also, what happens if the Accord cluster is split and then nodes are updated in each half of the split brain?
On Sun, Sep 25, 2011 at 2:49 PM, Flavio Junqueira <f...@yahoo-inc.com> wrote: > ZooKeeper returns ACK after writing the disks of the over half machines. >> Accord returns ACK after writing the disk of just one machine, which >> accepted a request. However, at the same time, the ACK assures that all >> servers receive the messages in the same order. >> The difference of the semantics means that this measurement is not fair. >> I would like to measure the under fair situation, but not yet. If there >> are requests from users, I'm going to implement it and measure it. Note >> that the benchmark of in-memory is fair. >> >> > I'm not sure I understand this part. You say that an operation is ACKed > after being written to one disk, but also that it is guaranteed to be > delivered in the same order in all servers. Does it mean that Accord still > replicates on other servers before ACKing but the other servers do not write > to disk? Otherwise, the first server may crash and never come back, and the > message cannot possibly be delivered by other servers. > > One question related to this point: with Accord, do you replicate the > original request message or the result of operation? Do you guarantee that > each server executes a request or applies the result of a request exactly > once? If not, what kind of semantics does Accord provide?
