Re: How can OpsCenter show me Read Request Latency where there are no read requests??

[Mikhail Panchenko]

I haven't used OpsCenter specifically, so this is a guess: often latency
metrics are based on the last N samples and what is graphed are percentiles
(as opposed to a sliding time window). That means that the graph will
remain the same until more requests occur, as the data that the percentiles
are calculated from is not changing (i.e. there are no new samples of
latency being added). If that's not it, then I don't know :D


On Tue, Jan 15, 2013 at 7:28 PM, Brian Tarbox tar...@cabotresearch.comwrote:

 I am making heavy use of DataStax OpsCenter to help tune my system and its
 great.

 And yet puzzling.  I see my clients do a burst of Reads causing the
 OpsCenter Read Requests chart to go up and stay up until the clients finish
 doing their reads.  The read request latency chart also goes upbut it
 stays up even after all the reads are done.  At last glance I've had next
 to zero reads for 10 minutes but still have a read request latency thats
 basically unchanged from when there were actual reads.

 How am I to interpret this?

 Thanks.

 Brian Tarbox

Re: Assertions running Cleanup on a 3-node cluster with Cassandra 1.1.4 and LCS

[Mikhail Panchenko]

Based on the steps outlined here
https://issues.apache.org/jira/browse/CASSANDRA-4644?focusedCommentId=13453156page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-13453156it
seems that LCS was not used until after 1.1.4 and they were able to do
a
full repair cleanup compact cycle on 1.1.4 before running into problems.

I don't see any major bugfixes for LCS in 1.1.5 either, so this appears to
be a legitimate bug if the timeline is correct.

On Tue, Sep 11, 2012 at 2:50 PM, Omid Aladini omidalad...@gmail.com wrote:

 On Tue, Sep 11, 2012 at 8:33 PM, Janne Jalkanen
 janne.jalka...@ecyrd.com wrote:
 
  A bug in Cassandra 1.1.2 and earlier could cause out-of-order sstables
  and inter-level overlaps in CFs with Leveled Compaction. Your sstables
  generated with 1.1.3 and later should not have this issue [1] [2].
 
  Does this mean that LCS on 1.0.x should be considered unsafe to
  use? I'm using them for semi-wide frequently-updated CounterColumns
  and they're performing much better on LCS than on STCS.

 That's true. Unsafe in the sense that your data might not be in the
 right shape with respect to order of keys in sstables and LCS's
 properties and you might need to offline-scrub when you upgrade to the
 latest 1.1.x.

  In case you have old Leveled-compacted sstables (generated with 1.1.2
  or earlier. including 1.0.x) you need to run offline scrub using
  Cassandra 1.1.4 or later via /bin/sstablescrub command so it'll fix
  out-of-order sstables and inter-level overlaps caused by previous
  versions of LCS. You need to take nodes down in order to run offline
  scrub.
 
  The  1.1.5 README does not mention this. Should it?

 The fix was released on 1.1.3 (LCS fix) and 1.1.4 (offline scrub) and
 I agree it would be helpful to have it on NEWS.txt.

 Cheers,
 Omid

  /Janne