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From Paulo Motta <pauloricard...@gmail.com>
Subject Re: nodetool repair uses option '-local' and '-pr' togather
Date Tue, 06 Sep 2016 03:25:57 GMT
You're right Christopher, I missed the fact that with RF=3 NTS will always
place a replica on us-east-1d, so in this case repair on this node would be
sufficient. Thanks for clarifying!

2016-09-05 11:28 GMT-03:00 Christopher Bradford <bradfordcp@gmail.com>:

> If each AZ has a different rack identifier and the keyspace uses
> NetworkTopologyStrategy with a replication factor of 3 then the single host
> in us-east-1d *will receive 100% of the data*. This is due
> to NetworkTopologyStrategy's preference for placing replicas across
> different racks before placing a second replica in a rack where data
> already resides. Check it out with CCM:
>
> > ccm node1 status
>
> Datacenter: us-east-1
> =====================
> Status=Up/Down
> |/ State=Normal/Leaving/Joining/Moving
> --  Address    Load       Tokens       Owns (effective)  Host ID
>                     Rack
> UN  127.0.0.1  98.31 KiB  1            40.0%
> a887ef23-c7ea-4f7a-94a4-1ed12b1caa38  us-east-1b
> UN  127.0.0.2  98.31 KiB  1            40.0%
> 30152aaa-cc5e-485d-9b98-1c51f1141155  us-east-1b
> UN  127.0.0.3  98.3 KiB   1            40.0%
> 8e1f68f7-571e-4479-bb1f-1ed526fefa9e  us-east-1c
> UN  127.0.0.4  98.31 KiB  1            40.0%
> 1c9b45ed-02ca-48b5-b619-a87107ff8eba  us-east-1c
> UN  127.0.0.5  98.31 KiB  1            40.0%
> 2a33751a-c718-44fc-8442-cce9996ebc0c  us-east-1d
>
> cqlsh> CREATE KEYSPACE replication_test WITH replication = {'class':
> 'NetworkTopologyStrategy', 'us-east-1': 3};
>
> > ccm node1 status replication_test
> Datacenter: us-east-1
> =====================
> Status=Up/Down
> |/ State=Normal/Leaving/Joining/Moving
> --  Address    Load       Tokens       Owns (effective)  Host ID
>                     Rack
> UN  127.0.0.1  88.38 KiB  1            80.0%
> a887ef23-c7ea-4f7a-94a4-1ed12b1caa38  us-east-1b
> UN  127.0.0.2  98.31 KiB  1            20.0%
> 30152aaa-cc5e-485d-9b98-1c51f1141155  us-east-1b
> UN  127.0.0.3  98.3 KiB   1            80.0%
> 8e1f68f7-571e-4479-bb1f-1ed526fefa9e  us-east-1c
> UN  127.0.0.4  98.31 KiB  1            20.0%
> 1c9b45ed-02ca-48b5-b619-a87107ff8eba  us-east-1c
> UN  127.0.0.5  98.31 KiB  1            100.0%
>  2a33751a-c718-44fc-8442-cce9996ebc0c  us-east-1d
>
> This can be tested further with a simple table and nodetool getendpoints.
>
> > ccm node1 nodetool getendpoints replication_test sample bar
>
> 127.0.0.2
> 127.0.0.3
> 127.0.0.5
>
> > ccm node1 nodetool getendpoints replication_test sample baz
>
> 127.0.0.1
> 127.0.0.3
> 127.0.0.5
>
> > ccm node1 nodetool getendpoints replication_test sample bif
>
> 127.0.0.3
> 127.0.0.5
> 127.0.0.1
>
> > ccm node1 nodetool getendpoints replication_test sample biz
>
> 127.0.0.2
> 127.0.0.3
> 127.0.0.5
>
> On Fri, Sep 2, 2016 at 9:41 AM Paulo Motta <pauloricardomg@gmail.com>
> wrote:
>
>> If I understand the way replication is done, the node in us-east-1d has
>> all the (data) replicas, right?
>>
>> No, for this to be correct, you'd need to have one DC per AZ, which is
>> not this case since you have a single DC encompassing multiple AZs. Right
>> now, replicas will be spread in 3 distinct AZs, which are represented as
>> racks in the single NTS DC if you are using EC2*Snitch. So your best bet is
>> probably to run repair -pr in all nodes.
>>
>>
>> 2016-09-01 14:28 GMT-03:00 Li, Guangxing <guangxing.li@pearson.com>:
>>
>>> Thanks for the info, Paulo.
>>>
>>> My cluster is in AWS, the keyspace has replication factor 3 with
>>> NetworkTopologyStrategy in one DC which have 5 nodes: 2 in us-east-1b, 2 in
>>> us-east-1c and 1 in us-east-1d. If I understand the way replication is
>>> done, the node in us-east-1d has all the (data) replicas, right? If so, if
>>> I do not use '-pr' option, would it be enough to run 'nodetool repair' ONLY
>>> on the node in us-east-1d? In other words, does 'nodetool repair' started
>>> on node in us-east-1d also cause repairs on replicas on other nodes? I am
>>> seeing different answers in discussion like this
>>> http://dba.stackexchange.com/questions/82414/do-you-hav
>>> e-to-run-nodetool-repair-on-every-node.
>>>
>>> Thanks again.
>>>
>>> George
>>>
>>> On Thu, Sep 1, 2016 at 10:22 AM, Paulo Motta <pauloricardomg@gmail.com>
>>> wrote:
>>>
>>>> https://issues.apache.org/jira/browse/CASSANDRA-7450
>>>>
>>>> 2016-09-01 13:11 GMT-03:00 Li, Guangxing <guangxing.li@pearson.com>:
>>>>
>>>>> Hi,
>>>>>
>>>>> I have a cluster running 2.0.9 with 2 data centers. I noticed that
>>>>> 'nodetool repair -pr keyspace cf' runs very slow (OpsCenter shows that
the
>>>>> node's data size is 39 GB and the largest SSTable size is like 7 GB so
the
>>>>> column family is not huge, SizeTieredCompactionStrategy is used). Repairing
>>>>> a column family on a single node takes over 5 hours. So I am wondering
if I
>>>>> can use option '-local' and '-pr' together, hoping to get some speed
up.
>>>>> But according to documentation at https://docs.datastax.com/e
>>>>> n/cassandra/2.0/cassandra/tools/toolsRepair.html '...Do not use -pr
>>>>> with this option to repair only a local data center...'. Can someone
tell
>>>>> me the reason why we should not use options '-local' and '-pr' together?
>>>>>
>>>>> Thanks.
>>>>>
>>>>> George
>>>>>
>>>>
>>>>
>>>
>>

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