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From Pierre Devops <>
Subject Slow bulk loading
Date Thu, 07 May 2015 08:44:53 GMT

I m streaming a big sstable using bulk loader of sstableloader but it's
very slow (3 Mbytes/sec) :

Summary statistics:
   Connections per host:         : 1
   Total files transferred:      : 1
   Total bytes transferred:      : 10357947484
   Total duration (ms):          : 3280229
   Average transfer rate (MB/s): : 3
   Peak transfer rate (MB/s):    : 3

I'm on a single node configuration, empty keyspace and table, with good
hardware 8x2.8ghz 32G RAM, dedicated to cassandra, so it's plenty of
ressource for the process. I'm uploading from another server.

The sstable is 9GB in size and have 4 partitions, but a lot of rows per
partition (like 100 millions), the clustering key is a INT and have 4 other
regulars columns, so approximatly 500 millions cells per ColumnFamily.

When I upload I notice one core of the cassandra node is full CPU (all
other cores are idleing), so I assume I'm CPU bound on node side. But why ?
What the node is doing ? Why does it take so long time ?

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