As our launch date approaches, I am getting increasingly nervous about
Cassandra tuning. It is a mysterious black art that I haven't mastered even
at the low usages that we have now. I know of a few more things I can do to
improve things, but how will I know if it is enough? All this is
particularl
If you want to do this, don´t use autoincrementing integers! ;o) Use UUID
instead. (or implement an stand alone id-server that handles autoincrement
savely)
2010/11/28 David Boxenhorn
> As our launch date approaches, I am getting increasingly nervous about
> Cassandra tuning. It is a mysterious
For the vast majority of my data usage eventual consistency is fine (i.e.
CL=ONE) but I have a small amount of critical data for which I read and
write using CL=QUORUM.
If I have a cluster with 3 nodes and RF=2, and CL=QUORUM does that mean that
a value can be read from or written to any 2 nodes,
to me it makes sense that if hinted handoff is off then cassandra cannot
satisfy 2 out of every 3rd writes writes when one of the nodes is down since
this node is the designated node of 2/3 writes.
But I don't remember reading this somewhere. Does hinted handoff affect
David's situation?
(David, di
On Sun, Nov 28, 2010 at 12:28 AM, David Boxenhorn wrote:
> As our launch date approaches, I am getting increasingly nervous about
> Cassandra tuning. It is a mysterious black art that I haven't mastered even
> at the low usages that we have now. I know of a few more things I can do to
> improve th
If you read/write data with quorum then you can safely take a node down in
this scenario. Subsequent writes will use hinted handoff to be passed to
the node when it comes back up.
More info is here: http://wiki.apache.org/cassandra/HintedHandoff
Does that answer your question?
-Jake
On Sun, N
Actually you can't. As explained in the wiki page linked:
"A hinted write does NOT count towards ConsistencyLevel requirements
of ONE, QUORUM, or ALL"
For CL.QUORUM, you do need QUORUM *replicas* to be alive to answer
the query. At RF=2, QUORUM=2 so no, you cannot take down any node
down or (some)
Thank you, Jake. It does... except that in another context you told me:
Hints only happen when a node is unavailable and you are writing with CL.ANY
If you never write with CL.ANY then you can turn off hinted handoff.
How do I reconcile this?
On Sun, Nov 28, 2010 at 7:11 PM, Jake Luciani wrote
On Sun, Nov 28, 2010 at 6:26 PM, David Boxenhorn wrote:
> Hints only happen when a node is unavailable and you are writing with CL.ANY
>
> If you never write with CL.ANY then you can turn off hinted handoff.
Hints happens at any consistency level. But they never helps to
reach the consistency lev
I was wrong on this scenario and I'll explain where I was incorrect.
Hints are stored for a downed node but they don't count towards meeting a
consistency level.
Let's take 2 scenarios:
RF=6, Nodes=10
If you READ/WRITE with CL.QUORUM you will need 4 alive nodes if one is down
it will still have
On Sun, Nov 28, 2010 at 11:35 AM, Tom Melendez wrote:
> On Sun, Nov 28, 2010 at 12:28 AM, David Boxenhorn wrote:
>> As our launch date approaches, I am getting increasingly nervous about
>> Cassandra tuning. It is a mysterious black art that I haven't mastered even
>> at the low usages that we ha
OK. To sum up: RF=2 and QUORUM are incompatible (if you want to be able to
take a node down).
Right?
On Sun, Nov 28, 2010 at 7:59 PM, Jake Luciani wrote:
> I was wrong on this scenario and I'll explain where I was incorrect.
>
> Hints are stored for a downed node but they don't count towards me
Right.
On Sun, Nov 28, 2010 at 1:03 PM, David Boxenhorn wrote:
> OK. To sum up: RF=2 and QUORUM are incompatible (if you want to be able to
> take a node down).
>
> Right?
>
> On Sun, Nov 28, 2010 at 7:59 PM, Jake Luciani wrote:
>
>> I was wrong on this scenario and I'll explain where I was inc
I'm not familiar with ulimit on RedHat systems, but are you sure you
have ulimit set correctly? Did you set it to '0' or 'unlimited'? I ask
because on a Debian system, I get this:
tho...@~ $ ulimit -l
unlimited
Where you said that you got back '0'.
- Tyler
On Sun, Nov 28, 2010 at 1:15 AM, Jaso
Ok that's a good point i will check - I am not sure.
Sent from my iPhone
On Nov 29, 2010, at 5:53, Tyler Hobbs wrote:
> I'm not familiar with ulimit on RedHat systems, but are you sure you
> have ulimit set correctly? Did you set it to '0' or 'unlimited'? I ask
> because on a Debian system, I
Put another way, "for RF=2, QUORUM is equivalent to ALL."
On Sun, Nov 28, 2010 at 12:03 PM, David Boxenhorn wrote:
> OK. To sum up: RF=2 and QUORUM are incompatible (if you want to be able to
> take a node down).
>
> Right?
--
Jonathan Ellis
Project Chair, Apache Cassandra
co-founder of Riptano
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