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From Jeff Jirsa <jeff.ji...@crowdstrike.com>
Subject Re: Removing a datacenter
Date Tue, 24 May 2016 16:43:32 GMT
The fundamental difference between a removenode and a decommission is which node(s) stream
data.

In decom, the leaving node streams.
In removenode, other owners of the data stream.

If you set replication factor for that DC to 0, there’s nothing to stream, so it’s irrelevant
– do whichever you like.




From:  Anubhav Kale
Reply-To:  "user@cassandra.apache.org"
Date:  Tuesday, May 24, 2016 at 9:03 AM
To:  "user@cassandra.apache.org"
Subject:  RE: Removing a datacenter

Sorry I should have more clear. What I meant was doing exactly what you wrote, but do a “removenode”
instead of “decommission” to make it even faster. Will that have any side-effect (I think
it shouldn’t) ?

 

From: Jeff Jirsa [mailto:jeff.jirsa@crowdstrike.com] 
Sent: Monday, May 23, 2016 4:43 PM
To: user@cassandra.apache.org
Subject: Re: Removing a datacenter

 

If you remove a node at a time, you’ll eventually end up with a single node in the DC you’re
decommissioning which will own all of the data, and you’ll likely overwhelm that node.

 

It’s typically recommended that you ALTER the keyspace, remove the replication settings
for that DC, and then you can decommission (and they won’t need to stream nearly as much,
since they no longer own that data – decom will go much faster).

 

 

 

From: Anubhav Kale
Reply-To: "user@cassandra.apache.org"
Date: Monday, May 23, 2016 at 4:41 PM
To: "user@cassandra.apache.org"
Subject: Removing a datacenter

 

Hello,

 

Suppose we have 2 DCs and we know that the data is correctly replicated in both. In such situation,
is it safe to “remove” one of the DCs by simply doing a “nodetool remove node” followed
by “nodetool removenode force” for each node in that DC (instead of doing a “nodetool
decommission” and waiting for it to finish) ?

 

Can someone confirm this won’t have any odd side-effects ?

 

Thanks !


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