Viewing profile — pbailis

Macrobase PI here – someone squatted on that io domain a long time ago while the project was active. Once we moved to macrobase.stanford.edu, a fan apparently took interest in our …

> Hmm... Serializable isolation and concurrency go together fine and certainly don't require blocking or even locking when using MVCC and optimistic concurrency. For that matter se…

Very cool, thanks! In general, immutable data items makes NBTA much easier; there's only one element in either 'good' or 'pending' for each data item at a time. The benefit of a si…

Good questions. In the example configuration in the post (i.e., two servers with no replication), during the period between the write start and end of phase two of writes, reads ca…

Ha--good catch! I don't know if anyone else noticed that. I meant to say "within 33-4.8% of the peak throughput..." That is, we're 95.2% of the peak, not 4.8% of the peak. Fixed, t…

Post author here. Interesting take, but I'm not sure I agree, or perhaps I misunderstand. In the initial example, I represented 'good' as a set for ease of understanding, but, in p…

Post author here. Hmm. The invariant we're trying to maintain is that any write in 'good' should have its transactional "siblings" in either 'good' or 'pending' on their respective…

Thanks for the feedback--these are great points. (post author, btw) > The problem to me seems to be that the interesting problems always come across the case where updates are not …

(edit: post author, [not OP]) here. Thanks for the feedback! > I guess one of the key insights is that each data has a canonical server owner which enforces the consistency of the …

I'll also add that the metadata requirements aren't huge--typically 8 bytes for the timestamp and N*(bytes per key) for the keys. In our implementation and the benchmarks that we p…

Good questions! > Doesn't writes that commute mean that there was no contention to begin with? Ideally, if I have a balance of $100 in my account and try to spend $60 in two differ…

> Does the data remain stable, or must some additional work be performed to correct the inconsistent state? If you want client writes that reached all servers to become visible, th…

> However it doesn't appear to directly include semantics for aborting transactions which is a pretty important part of a distributed transaction protocol. Yep, I left this out to …

Yep--thanks! I've updated the post accordingly :)

There's at least one good reason for Dynamo's write-to-all and read-from-all mechanism: latency. What you've called 'W=2' in Couchbase is "write to master and at least one slave." …

> if I understand correctly there's no way to avoid an extra round trip? With HATs, you only need to contact one replica for every key. This is to goal behind our definition of "hi…

Good point, and well-taken. As I mention in http://www.bailis.org/blog/hat-not-cap-introducing-highly-av... (and devote an full section to in the paper, including documented isolat…

I think we're conflating Snapshot Isolation and MVCC (e.g., Snapshot-isolation/MVCC ). MVCC is a general concurrency control mechanism, not an isolation level. Coupling MVCC and Sn…

there are still fairly hard guarantees about things like consistency that you get with other isolation levels What do you mean by consistency ? I agree that there are many ways to …

Good points on both sides. One thing I'll point out is that many clustering, HA, and multi-master replication solutions either rely on a single master (what I think Michael means w…

Unlike "C" and "A" in "CAP," "AC&D" (specifically, "C") can't be easily separated from "I". Serializability ("I") ensures that database consistency, or maintenance of integrity con…