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From Benjamin Reed <br...@yahoo-inc.com>
Subject Re: size of data / number of znodes
Date Tue, 15 Dec 2009 15:51:34 GMT
there aren't any limits on the number of znodes, it's just limited by 
your memory. there are two things (probably more :) to keep in mind:

1) the 1M limit also applies to the children list. you can't grow the 
list of children to more than 1M (the sum of the names of all of the 
children) otherwise you cannot to a getChildren(). so, yes, you need to 
do some bucketing to keep the number of children to something 
reasonable. assuming your names will be less than 100 bytes, you 
probably want to limit the number of children to 10,000.

2) since there are times that you need to do a state transfer between 
servers (dump all the state from one to the other to bring it online) it 
may take a while depending on your network speed. you may need to bump 
up the default initLimit, so make sure you do some benchmarking on your 
platform to test your configuration parameters.


Michael Bauland wrote:
> Hello,
> I'm new to the Zookeeper project and wondering whether our use case is a
> good one for Zookeeper. I read the documentation, but couldn't find an
> answer. At some point it says that
>> A common property of the various forms of coordination data is that they are relatively
small: measured in kilobytes. The ZooKeeper client and the server implementations have sanity
checks to ensure that znodes have less than 1M of data
> I couldn't find any limits on the number of znodes used, only that each
> znode should only contain little data. We were planning to use a million
> znodes (each containing a few hundred bytes of data). Would this use
> case be acceptable for Zookeeper? And if so, does it matter if we have a
> flat hierarchy (i.e, all nodes have the root node as their direct
> ancestor) or should we introduce some (artificial) hierarchy levels to
> have a more tree-like structure?
> Thanks in advance for your answer.
> Cheers,
> Michael

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