cassandra-user mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From kannan chandrasekaran <>
Subject Re: Couple of cache related questions
Date Tue, 14 Sep 2010 17:32:35 GMT
Thanks a lot Jonathan !!!


From: Jonathan Ellis <>
Sent: Mon, September 13, 2010 4:47:05 PM
Subject: Re: Couple of cache related questions

On Sun, Sep 12, 2010 at 6:10 PM, kannan chandrasekaran
<> wrote:
>> 1) What determines the amount of memory used per schema ignoring the
>> general
>> overhead to get cassandra up and running?  Is it just the size of the
>> caches
>> for the column Family + the memtable size ?
> and the bloom filter and index samples from the sstable files.
> Does that mean that cassandra tries to load the index and filter tables in
> memory as well, for each sstable in the keyspace?

it means it loads the bloom filter file, and a sample from the index file.

> Once the final memtable is flushed to the disk ( assuming no more writes) ,
> does read path also incur the memory size of the memtable for that
> particular CF ?


> Does cassandra try to preallocate memory after startup for each schema even
> if its not used ( not being currently written to or read from)  ?


> If I understand you correctly then I need to make sure that
>  the sum of sizes of all items in the cache across all the keyspaces +
> memtable + bloom filter + index samples  < Heap space


Jonathan Ellis
Project Chair, Apache Cassandra
co-founder of Riptano, the source for professional Cassandra support

View raw message