On Mon, Dec 28, 2015 at 5:57 PM, xutom <xutom2006@126.com> wrote:
    I have 5 nodes in my C* cluster, and each node has the same configuration file(Cassandra-env.sh: MAX_HEAP_SIZE="32G" and HEAP_NEWSIZE="8G"), and My Cassandra version is 2.1.1. Now I want to export all data of one table, i am using  select * from tablename,

Probably lower your heap size. If you're using CMS GC with 32gb heap you will get long GC pauses.

Also use a modern CQL client with paging support.

In addition, upgrade to the head of 2.1.x, 2.1.1 is not a version anyone should be using in production at this time.

=Rob