Rebalance a cassandra cluster

[Akshit Jain <ak...@iiitd.ac.in>]

Hi,
Can a cassandra cluster be unbalanced in terms of data?
If yes then how to rebalance a cassandra cluster.

Re: Rebalance a cassandra cluster

[Akshit Jain <ak...@iiitd.ac.in>]

Suppose I have a cassandra cluster with the data that is skewed such that
one node have 40% more data than other nodes.Since while creating the
cassandra the tokens were distributed uniformly.
Now to make the data uniform I have to recalculate the tokens and assign
them to nodes in the cluster. Then run repair and cleanup.
The question is How to recalculate the tokens and assign them to
nodes(Keeping cost ,distance between nodes and data movement in mind)

Regards
Akshit Jain
B-Tech,2013124
9891724697


On Wed, Sep 13, 2017 at 11:54 AM, Hannu Kröger <hk...@gmail.com> wrote:

> Hi,
>
> you should make sure that token range is evenly distributed if you have a
> single token configured per node. You can use e.g. this tool to calculate
> tokens:
> https://www.geroba.com/cassandra/cassandra-token-calculator/
>
> Also, make sure that none of the partitions in your data model are
> hotspots that contain a lot more data than on average. Check also
> materialized views if you use them.
>
> Also, due to way the compactions work, it’s normal that the disk usage
> goes up and down. Since nodes often do that in different rhythms, you
> always see that some node(s) are using more disk space than others if some
> point of time especially if you do updates&deletes and not just inserts.
>
> Cheers,
> Hannu
>
> On 13 September 2017 at 07:47:09, Akshit Jain (akshit13124@iiitd.ac.in)
> wrote:
>
> Hi,
> Can a cassandra cluster be unbalanced in terms of data?
> If yes then how to rebalance a cassandra cluster.
>
>

Re: Rebalance a cassandra cluster

[Hannu Kröger <hk...@gmail.com>]

Hi,

you should make sure that token range is evenly distributed if you have a
single token configured per node. You can use e.g. this tool to calculate
tokens:
https://www.geroba.com/cassandra/cassandra-token-calculator/

Also, make sure that none of the partitions in your data model are hotspots
that contain a lot more data than on average. Check also materialized views
if you use them.

Also, due to way the compactions work, it’s normal that the disk usage goes
up and down. Since nodes often do that in different rhythms, you always see
that some node(s) are using more disk space than others if some point of
time especially if you do updates&deletes and not just inserts.

Cheers,
Hannu

On 13 September 2017 at 07:47:09, Akshit Jain (akshit13124@iiitd.ac.in)
wrote:

Hi,
Can a cassandra cluster be unbalanced in terms of data?
If yes then how to rebalance a cassandra cluster.

RE: Rebalance a cassandra cluster

["Harika Vangapelli -T (hvangape - AKRAYA INC at Cisco)" <hv...@cisco.com>]

Check with nodetool repair.

[http://wwwin.cisco.com/c/dam/cec/organizations/gmcc/services-tools/signaturetool/images/logo/logo_gradient.png]



Harika Vangapelli
Engineer - IT
hvangape@cisco.com<ma...@cisco.com>
Tel:

Cisco Systems, Inc.



United States
cisco.com


[http://www.cisco.com/assets/swa/img/thinkbeforeyouprint.gif]Think before you print.

This email may contain confidential and privileged material for the sole use of the intended recipient. Any review, use, distribution or disclosure by others is strictly prohibited. If you are not the intended recipient (or authorized to receive for the recipient), please contact the sender by reply email and delete all copies of this message.
Please click here<http://www.cisco.com/web/about/doing_business/legal/cri/index.html> for Company Registration Information.


From: Akshit Jain [mailto:akshit13124@iiitd.ac.in]
Sent: Tuesday, September 12, 2017 9:47 PM
To: user@cassandra.apache.org
Subject: Rebalance a cassandra cluster

Hi,
Can a cassandra cluster be unbalanced in terms of data?
If yes then how to rebalance a cassandra cluster.