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From: Jonathan Ellis <jbellis@gmail.com>
Date: Tue, 23 Feb 2010 07:31:46 -0600
Message-ID: <e06563881002230531r4205a6eama0deeb70bddc6df2@mail.gmail.com>
Subject: Re: problem about bootstrapping when used in huge node
To: cassandra-user@incubator.apache.org
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On Tue, Feb 23, 2010 at 12:33 AM, Michael Lee
<mail.list.steel.mental@gmail.com> wrote:
> (1)=A0=A0=A0=A0 A cluster cannot be enlarge(add more node into cluster) i=
f it
> already used more than half capacity:
>
> If every node has data more than it=92s half capacity , the admin may not
> bootstrapping new node into cluster,
>
> because old nodes must strip data belong to new node through
> anti-compaction, the process will create a large tmp SSTable
> file (for streaming), which may large than free disk space ( of one node =
).

That's right, in the worst case.  On average, any node sending to a
bootstrap node will only have to anti-compact half its data.

We have https://issues.apache.org/jira/browse/CASSANDRA-579 open to
allow streaming data w/o first writing it locally.

> (1)     Is cassandra designed to waste half of it=92s capacity?

Yes, although I might describe it as "cassandra requires up to half
its capacity as temporary space for compaction and anticompaction."
http://wiki.apache.org/cassandra/MemtableSSTable

That's the price you pay for no random writes.

> (2)=A0=A0=A0=A0 How to use node has 12 1TB disk??

You should use a better filesystem than ext3. :)  We use xfs at rackspace.

-Jonathan