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From Jonathan Lacefield <>
Subject Re: High read latency after data volume increased
Date Mon, 12 Jan 2015 13:05:27 GMT
There's likely 2 things occurring

1) the cfhistograms error is due to
Which is resolved in 2.1.3.  Looks like voting is under way for 2.1.3. As
rcoli mentioned, you are running the latest open source of C* which should
be treated as beta until a few dot releases are published.

2) compaction running all the time doesn't mean that compaction is "caught
up".  It's possible that the nodes are behind in compaction which will
cause slow reads.  C* read performance is typically associated with disk
system performance, both to service reads from disk as well as to enable
fast background processing, like compaction.   You mentioned raided hdds.
What type of raid is configured?  How fast are your disks responding?  You
may want to check iostat to see how large your queues and awaits are.  If
the await is high, then you could be experiencing disk perf issues
impacting reads.

Hope this helps

On Jan 9, 2015, at 9:29 AM, Roni Balthazar <> wrote:

Hi there,

The compaction remains running with our workload.
We are using SATA HDDs RAIDs.

When trying to run cfhistograms on our user_data table, we are getting
this message:
nodetool: Unable to compute when histogram overflowed

Please see what happens when running some queries on this cf:


Roni Balthazar

On Fri, Jan 9, 2015 at 12:03 PM, datastax <> wrote:


 You may not be experiencing versioning issues.   Do you know if compaction

is keeping up with your workload?  The behavior described in the subject is

typically associated with compaction falling behind or having a suboptimal

compaction strategy configured.   What does the output of nodetool

cfhistograms <keyspace> <table> look like for a table that is experiencing

this issue?  Also, what type of disks are you using on the nodes?

Sent from my iPad

On Jan 9, 2015, at 8:55 AM, Brian Tarbox <> wrote:

C* seems to have more than its share of "version x doesn't work, use version

y " type issues....

On Thu, Jan 8, 2015 at 2:23 PM, Robert Coli <> wrote:

On Thu, Jan 8, 2015 at 11:14 AM, Roni Balthazar <>


We are using C* 2.1.2 with 2 DCs. 30 nodes DC1 and 10 nodes DC2.

2.1.2 in particular is known to have significant issues. You'd be better

off running 2.1.1 ...



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