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From Daniel Doubleday <>
Subject Re: cassandra nodes with mixed hard disk sizes
Date Tue, 22 Mar 2011 09:54:44 GMT

On Mar 22, 2011, at 5:09 AM, aaron morton wrote:

> 1) You should use nodes with the same capacity (CPU, RAM, HDD), cassandra assumes they
are all equal. 

Care to elaborate? While equal node will certainly make life easier I would have thought that
 dynamic snitch would take care of performance differences and manual assignment of token
ranges can yield to any data distribution. Obviously if a node has twice as much data will
probably get twice the load. But if that is no problem ...

Where does cassandra assume that all are equal?  

Cheers Daniel

> 2) Not sure what exactly would happen. Am guessing either the node would shutdown or
writes would eventually block, probably the former. If the node was up read performance may
suffer (if there were more writes been sent in). If you really want to know more let me know
and I may find time to dig into it. 
> Also a node is be responsible for storing it's token range and acting as a replica for
other token ranges. So reducing the token range may not have a dramatic affect on the storage
> Hope that helps. 
> Aaron
> On 22 Mar 2011, at 09:50, Jonathan Colby wrote:
>> This is a two part question ...
>> 1. If you have cassandra nodes with different sized hard disks,  how do you deal
with assigning the token ring such that the nodes with larger disks get more data?   In other
words, given equally distributed token ranges, when the smaller disk nodes run out of space,
the larger disk nodes with still have unused capacity.    Or is installing a mixed hardware
cluster a no-no?
>> 2. What happens when a cassandra node runs out of disk space for its data files?
 Does it continue serving the data while not accepting new data?  Or does the node break and
require manual intervention?
>> This info has alluded me elsewhere.
>> Jon

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