[jira] [Resolved] (CASSANDRA-9323) Bulk loading is slow

["Jonathan Ellis (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/CASSANDRA-9323?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Jonathan Ellis resolved CASSANDRA-9323.
---------------------------------------
       Resolution: Won't Fix
    Fix Version/s:     (was: 2.1.x)

The preferred way to bulk load is now COPY; see CASSANDRA-11053 and linked tickets.

> Bulk loading is slow
> --------------------
>
>                 Key: CASSANDRA-9323
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-9323
>             Project: Cassandra
>          Issue Type: Improvement
>            Reporter: Pierre N.
>         Attachments: App.java
>
>
> When I bulk upload sstable created with CQLSSTableWriter, it's very slow. I tested on a fresh cassandra node (nothing in keyspace, nor tables) with good hardware (8x2.8ghz, 32G ram), but with classic hard disk (performance won't be improved with SSD in this case I think). 
> When I upload from a different server an sstable using sstableloader I get an average of 3 MB/sec, in the attached example I managed to get 5 MB/sec, which is still slow.
> During the streaming process  I noticed that one core of the server is full CPU, so I think the operation is CPU bound server side. I quickly attached a sample profiler to the cassandra instance and got the following output : 
> https://i.imgur.com/IfLc2Ip.png
> So, I think, but I may be wrong because it's inaccurate sampling, during streaming the table is unserialized and reserialized to another sstable, and that's this unserialize/serialize process which is taking a big amount of CPU, slowing down the insert speed.
> Can someone confirm the bulk load is slow ? I tested also on my computer and barely reach 1MB/sec 
> I don't understand the point of totally unserializing the table I just did build using the CQLSStableWriter (because it's already a long process to build and sort the table), couldn't it just copy the table from offset X to offset Y (using index information by example) without unserializing/reserializing it ?



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