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From Brian Burruss <bburr...@real.com>
Subject RE: read latency creaping up
Date Sun, 13 Dec 2009 21:18:58 GMT
if this isn't a known issue, lemme do some more investigating.  my test client becomes "more
random" with reads as time progresses, so possibly this is what causes the latency issue.
 however, all that being said, the performance really becomes bad after a while.

________________________________________
From: Brian Burruss
Sent: Sunday, December 13, 2009 1:14 PM
To: cassandra-user@incubator.apache.org
Subject: read latency creaping up

i've noticed the longer i let my test clients run the higher the read latency becomes.  if
i kill the clients, the latency drops back down to a reasonable value.  write latency isn't
affected.  here are two cfstats listings from the same machine, the first before and the second
after i killed the clients.  i do not touch the servers.  this seems odd.  if the clients
are doing some bad, it seems that the server's latency wouldn't be affected.  is this a thrift
issue?

before
---------


Keyspace: uds
        Read Count: 2003
        Read Latency: 59.807 ms.
        Write Count: 65145
        Write Latency: 0.047 ms.
        Pending Tasks: 0
                Column Family: bucket
                Memtable Columns Count: 168751
                Memtable Data Size: 351695390
                Memtable Switch Count: 94
                Read Count: 2003
                Read Latency: 59.807 ms.
                Write Count: 65176
                Write Latency: 0.047 ms.
                Pending Tasks: 0


after
-------

Keyspace: uds
        Read Count: 53249
        Read Latency: 3.653 ms.
        Write Count: 52888
        Write Latency: 0.035 ms.
        Pending Tasks: 0
                Column Family: bucket
                Memtable Columns Count: 383297
                Memtable Data Size: 798864312
                Memtable Switch Count: 94
                Read Count: 53271
                Read Latency: 3.649 ms.
                Write Count: 52937
                Write Latency: 0.035 ms.
                Pending Tasks: 0

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