Re: Rack Awareness

[kurt greaves]

Cassandra understands racks based on the configured snitch and the rack
assigned to each node (for example in cassandra-rackdc.properties if using
GossipingPropertyFileSnitch). If you have racks configured, to perform a
"rack-aware" repair you would simply need to run repair on only one rack.
Note that there is no real concept of a "rack-aware" repair, it's just a
side effect of the replication strategy and topology choices you make.​

Re: Rack Awareness

[Jeff Jirsa]

What command exactly do you think gives you a rack-aware repair?


On Tue, Aug 29, 2017 at 11:52 AM, Mark Furlong 
wrote:

> I am getting ready to start what I understand as a rack aware repair. This
> is to run the repair on each node within the rack resulting in a repair of
> the entire cluster. My question comes due to a highly out of balance set of
> racks and I want to know if Cassandra 2.1.12 is smart enough to identify
> the racks by the rack value or by the ip address?
>
>
>
> *Mark Furlong*
>
> Sr. Database Administrator
>
> *mfurl...@ancestry.com *
> M: 801-859-7427 <(801)%20859-7427>
>
> O: 801-705-7115 <(801)%20705-7115>
>
> 1300 W Traverse Pkwy
>
> Lehi, UT 84043
>
>
>
>
>
> ​[image: http://c.mfcreative.com/mars/email/shared-icon/sig-logo.gif]
>
>
>
>
>

Rack Awareness

[Mark Furlong]

I am getting ready to start what I understand as a rack aware repair. This is 
to run the repair on each node within the rack resulting in a repair of the 
entire cluster. My question comes due to a highly out of balance set of racks 
and I want to know if Cassandra 2.1.12 is smart enough to identify the racks by 
the rack value or by the ip address?

Mark Furlong

Sr. Database Administrator

mfurl...@ancestry.com
M: 801-859-7427
O: 801-705-7115
1300 W Traverse Pkwy
Lehi, UT 84043





​[http://c.mfcreative.com/mars/email/shared-icon/sig-logo.gif]

Re: Cassandra rack awareness

[Amlan Roy]

Hi Rob,

Thanks for sharing the link. I have gone through it and few other documents as 
well. Still I am confused. It seems, if we use vnodes and 
NetworkTopologyStrategy, we should use a single rack configuration in 
Cassandra. Or, it can create hotspots in the ring. Not sure if my understanding 
is correct.

Regards.


On 28-Feb-2015, at 2:42 am, Robert Coli rc...@eventbrite.com wrote:

 On Fri, Feb 27, 2015 at 7:30 AM, Amlan Roy amlan@cleartrip.com wrote:
 I am new to Cassandra and trying to setup a Cassandra 2.0 cluster using 4 
 nodes, 2 each in 2 different racks. All are in same data centre. This is what 
 I see in the documentation:
 
 To use racks correctly:
 
 Use the same number of nodes in each rack. Use one rack and place the nodes 
 in different racks in an alternating pattern. This allows you to still get 
 the benefits of Cassandra's rack feature, and allows for quick and fully 
 functional expansions. Once the cluster is stable, you can swap nodes and 
 make the appropriate moves to ensure that nodes are placed in the ring in an 
 alternating fashion with respect to the racks.
 What I have understood is, in cassandra-rackdc.properties, I need to use 
 single rack name even though I have 2 racks and then place the nodes in such 
 an order that they are placed in an alternating fashion - RAC1-NODE1, 
 RAC2-NODE1, RAC1-NODE2, RAC2-NODE2.
 
 Just wanted to know if this is correct. If yes, how do I enforce this order 
 while adding nodes.
 
 https://issues.apache.org/jira/browse/CASSANDRA-3810
 
 =Rob
  

Re: Cassandra rack awareness

[Edson Marquezani Filho]

As far as I know, the main thing about using NetworkTopologyStrategy
and different racks is replica placement throughout your cluster. That
strategy favours different racks when it comes to choosing where a
row's replica will be placed. So, if you have different numbers of
nodes in each rack, you will probably end up with an unbalanced
cluster (regarding data occupation), not because of the actual rows
partitioning, but because of the replicas. The effects of it also
depends on you replication factor. (You can sit down and do the math
yourself.)

I had an issue like that sometime ago, because I was not aware of that
behavior and didn't really care about where my machines were, and was
using SimpleStrategy. But when I decided to go for
NetworkTopologyStrategy, I realized I had a bad physical configuration
(4 nodes in a same rack, 1 node in another one), so I had to fake that
last node's rack, as if it was in the same as the other nodes,
otherwise I would have that node alone in the rack with twice the data
amount the other ones had. (As I said, that could even be worse if I
had a higher replication factor.)

To be honest, I'm not sure I fully understand the documentation you
quoted on your first email, specially the last phrase. But, my
(limited) experience with Cassandra (2.1) tells me that if you start
off with a balanced rack setup, I'll be fine. Otherwise, you'll have
to change you node's physical localization or faking it on config
file, and run repair and clean on your entire cluster (which is a pain
in the ass) to get a balanced cluster again. I had to do that. =P

On Sat, Feb 28, 2015 at 6:05 AM, Amlan Roy amlan@cleartrip.com wrote:
 Hi Rob,

 Thanks for sharing the link. I have gone through it and few other documents
 as well. Still I am confused. It seems, if we use vnodes and
 NetworkTopologyStrategy, we should use a single rack configuration in
 Cassandra. Or, it can create hotspots in the ring. Not sure if my
 understanding is correct.

 Regards.


 On 28-Feb-2015, at 2:42 am, Robert Coli rc...@eventbrite.com wrote:

 On Fri, Feb 27, 2015 at 7:30 AM, Amlan Roy amlan@cleartrip.com wrote:

 I am new to Cassandra and trying to setup a Cassandra 2.0 cluster using 4
 nodes, 2 each in 2 different racks. All are in same data centre. This is
 what I see in the documentation:

 To use racks correctly:

 Use the same number of nodes in each rack. Use one rack and place the
 nodes in different racks in an alternating pattern. This allows you to still
 get the benefits of Cassandra's rack feature, and allows for quick and fully
 functional expansions. Once the cluster is stable, you can swap nodes and
 make the appropriate moves to ensure that nodes are placed in the ring in an
 alternating fashion with respect to the racks.

 What I have understood is, in cassandra-rackdc.properties, I need to use
 single rack name even though I have 2 racks and then place the nodes in such
 an order that they are placed in an alternating fashion - RAC1-NODE1,
 RAC2-NODE1, RAC1-NODE2, RAC2-NODE2.

 Just wanted to know if this is correct. If yes, how do I enforce this
 order while adding nodes.

 https://issues.apache.org/jira/browse/CASSANDRA-3810

 =Rob

Cassandra rack awareness

[Amlan Roy]

Hi,

I am new to Cassandra and trying to setup a Cassandra 2.0 cluster using 4 
nodes, 2 each in 2 different racks. All are in same data centre. This is what I 
see in the documentation:

To use racks correctly:

Use the same number of nodes in each rack. Use one rack and place the nodes in 
different racks in an alternating pattern. This allows you to still get the 
benefits of Cassandra's rack feature, and allows for quick and fully functional 
expansions. Once the cluster is stable, you can swap nodes and make the 
appropriate moves to ensure that nodes are placed in the ring in an alternating 
fashion with respect to the racks.
What I have understood is, in cassandra-rackdc.properties, I need to use single 
rack name even though I have 2 racks and then place the nodes in such an order 
that they are placed in an alternating fashion - RAC1-NODE1, RAC2-NODE1, 
RAC1-NODE2, RAC2-NODE2.

Just wanted to know if this is correct. If yes, how do I enforce this order 
while adding nodes.

Thanks.

Re: Cassandra rack awareness

[Robert Coli]

On Fri, Feb 27, 2015 at 7:30 AM, Amlan Roy amlan@cleartrip.com wrote:

 I am new to Cassandra and trying to setup a Cassandra 2.0 cluster using 4
 nodes, 2 each in 2 different racks. All are in same data centre. This is
 what I see in the documentation:

 To use racks correctly:
 Use the same number of nodes in each rack. Use one rack and place the
 nodes in different racks in an alternating pattern. This allows you to
 still get the benefits of Cassandra's rack feature, and allows for quick
 and fully functional expansions. Once the cluster is stable, you can swap
 nodes and make the appropriate moves to ensure that nodes are placed in the
 ring in an alternating fashion with respect to the racks.

 What I have understood is, in cassandra-rackdc.properties, I need to use
 single rack name even though I have 2 racks and then place the nodes in
 such an order that they are placed in an alternating fashion - RAC1-NODE1,
 RAC2-NODE1, RAC1-NODE2, RAC2-NODE2.

 Just wanted to know if this is correct. If yes, how do I enforce this
 order while adding nodes.

https://issues.apache.org/jira/browse/CASSANDRA-3810

=Rob