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Date: Tue, 21 Sep 2010 14:11:32 -0400 (EDT)
From: "Stu Hood (JIRA)" <jira@apache.org>
To: commits@cassandra.apache.org
Subject: [jira] Commented: (CASSANDRA-1526) Make cassandra sampling and
 startup faster
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    [ https://issues.apache.org/jira/browse/CASSANDRA-1526?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12913136#action_12913136 ] 

Stu Hood commented on CASSANDRA-1526:
-------------------------------------

> Since SSTables are immutable is there a way the sampling of the tables could be saved?
Yes, this is definitely feasible, and much easier in 0.7.

> Make cassandra sampling and startup faster
> ------------------------------------------
>
>                 Key: CASSANDRA-1526
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-1526
>             Project: Cassandra
>          Issue Type: New Feature
>            Reporter: Edward Capriolo
>
> http://wiki.apache.org/cassandra/CassandraHardware makes mention of very large disks I do not see how that would be possible.
> We have a server class system have 4x processors 16GB RAM a 6 DISK RAID5 (yes RAID0 would be faster but still) 
> {noformat}
> INFO [main] 2010-09-21 12:58:26,348 SSTableReader.java (line 120) Sampling index for /var/lib/cassandra/data/system/LocationInfo-699-Data.db
> ...
> INFO [main] 2010-09-21 13:05:51,333 CassandraDaemon.java (line 124) Binding thrift service to cdbsd07/10.71.71.57:9160
> {noformat}
> This node has 200GB of data in two column families and the time to sample all tables and startup is 7+ minutes. The logging suggests this process is happening a single SSTable at a time. Additionally the normal system vitals mainly DISK and CPU do not look overtaxed.
> * Since SSTables are immutable is there a way the sampling of the tables could be saved?
> * Could this process be done in parallel for speedup?
> * Can multiple column families be processed at once?
> Unless someone has an insanely powerful disk pack making mention of 2TB limitations seem out of place. Unless my calculations are wrong (which they usually are), I have a pretty decent hardware, and if I had 2 TB of data I would have a 95 minute node start up? 
> I hope that maybe sampling multiple ColumnFamilies at once would make nodes of at least a few hundred GB startup reasonably fast.

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