incubator-cassandra-user mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Timo Nentwig <timo.nent...@toptarif.de>
Subject Re: Quorum: killing 1 out of 3 server kills the cluster (?)
Date Thu, 09 Dec 2010 16:43:41 GMT

On Dec 9, 2010, at 17:39, David Boxenhorn wrote:

> In other words, if you want to use QUORUM, you need to set RF>=3. 
> 
> (I know because I had exactly the same problem.) 

I naively assume that if I kill either node that holds N1 (i.e. node 1 or 3), N1 will still
remain on another node. Only if both fail, I actually lose data. But apparently this is not
how it works...

> On Thu, Dec 9, 2010 at 6:05 PM, Sylvain Lebresne <sylvain@yakaz.com> wrote:
> I'ts 2 out of the number of replicas, not the number of nodes. At RF=2, you have
> 2 replicas. And since quorum is also 2 with that replication factor,
> you cannot lose
> a node, otherwise some query will end up as UnavailableException.
> 
> Again, this is not related to the total number of nodes. Even with 200
> nodes, if
> you use RF=2, you will have some query that fail (altough much less that what
> you are probably seeing).
> 
> On Thu, Dec 9, 2010 at 5:00 PM, Timo Nentwig <timo.nentwig@toptarif.de> wrote:
> >
> > On Dec 9, 2010, at 16:50, Daniel Lundin wrote:
> >
> >> Quorum is really only useful when RF > 2, since the for a quorum to
> >> succeed RF/2+1 replicas must be available.
> >
> > 2/2+1==2 and I killed 1 of 3, so... don't get it.
> >
> >> This means for RF = 2, consistency levels QUORUM and ALL yield the same result.
> >>
> >> /d
> >>
> >> On Thu, Dec 9, 2010 at 4:40 PM, Timo Nentwig <timo.nentwig@toptarif.de>
wrote:
> >>> Hi!
> >>>
> >>> I've 3 servers running (0.7rc1) with a replication_factor of 2 and use quorum
for writes. But when I shut down one of them UnavailableExceptions are thrown. Why is that?
Isn't that the sense of quorum and a fault-tolerant DB that it continues with the remaining
2 nodes and redistributes the data to the broken one as soons as its up again?
> >>>
> >>> What may I be doing wrong?
> >>>
> >>> thx
> >>> tcn
> >
> >
> 


Mime
View raw message