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From Ted Dunning <ted.dunn...@gmail.com>
Subject Re: [announce] Accord: A high-performance coordination service for write-intensive workloads
Date Sun, 25 Sep 2011 22:26:27 GMT
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 <fpj@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?

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