A read repair will fix it immediately after the first read of the row. On 2010-04-08 16:36, Mark Greene wrote: > So unless you re-try the write, the previous stale write stays on the > other two nodes? Would a read repair fix this eventually? > > On Thu, Apr 8, 2010 at 11:36 AM, Avinash Lakshman > <avinash.laksh...@gmail.com <mailto:avinash.laksh...@gmail.com>> wrote: > > What your describing is a distributed transaction? Generally strong > consistency is always associated with doing transactional writes > where you never see the results of a failed write on a subsequent > read no matter what happens. Cassandra has no notion of rollback. > That is why no combination will give you strong consistency. The > idea is you re-try the failed write and eventually the system would > have gotten rid of the previous stale write. > > Avinash > > > On Thu, Apr 8, 2010 at 8:29 AM, Jeremy Dunck <jdu...@gmail.com > <mailto:jdu...@gmail.com>> wrote: > > On Thu, Apr 8, 2010 at 7:16 AM, Gary Dusbabek > <gdusba...@gmail.com <mailto:gdusba...@gmail.com>> wrote: > > On Thu, Apr 8, 2010 at 02:55, Paul Prescod <p...@ayogo.com > <mailto:p...@ayogo.com>> wrote: > >> In this¹ debate, there seemed to be consensus on the > following fact: > >> > >> "In Cassandra, say you use N=3, W=3 & R=1. Let’s say you > managed to > >> only write to replicas A & B, but not C. In this case > Cassandra will > >> return an error to the application saying the write failed- > which is > >> acceptable given than W=3. But Cassandra does not > cleanup/rollback the > >> writes that happened to A & B." > >> > > > > correct: no rolling back. Cassandra does go out of its way to > make > > sure the cluster is healthy enough to begin the write though. > > I think the general answer here is don't use R=1 if you can't > tolerate > inconsistency? Still the point of confusion -- if W=3 and the write > succeeds on 2 nodes but fails the 3rd, the write fails (to the > updating client), but is the data on the two successful nodes still > readable (i.e. reading from what was actually a failed write)? > > >
-- David Strauss | da...@fourkitchens.com | +1 512 577 5827 [mobile] Four Kitchens | http://fourkitchens.com | +1 512 454 6659 [office] | +1 512 870 8453 [direct]
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