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From Apache Wiki <wikidi...@apache.org>
Subject [Cassandra Wiki] Update of "FAQ" by thepaul
Date Tue, 19 Jul 2011 21:37:58 GMT
Dear Wiki user,

You have subscribed to a wiki page or wiki category on "Cassandra Wiki" for change notification.

The "FAQ" page has been changed by thepaul:
http://wiki.apache.org/cassandra/FAQ?action=diff&rev1=124&rev2=125

Comment:
note that problem also existed on bare metal

   * [[#seed_spof|Does single seed mean single point of failure?]]
   * [[#jconsole_array_arg|Why can't I call jmx method X on jconsole? (ex. getNaturalEndpoints)]]
   * [[#max_key_size|What's the maximum key size permitted?]]
-  * [[#ubuntu_ec2_hangs|I'm using Ubuntu on EC2 with JNA, and holy crap weird things keep
hanging and stalling and printing scary tracebacks in dmesg!]]
+  * [[#ubuntu_hangs|I'm using Ubuntu with JNA, and holy crap weird things keep hanging and
stalling and printing scary tracebacks in dmesg!]]
  
  <<Anchor(cant_listen_on_ip_any)>>
  
@@ -478, +478 @@

  Routing is O(N) of the key size and querying and updating are O(N log N). In practice these
factors are usually dwarfed by other overhead, but some users with very large "natural" keys
use their hashes instead to cut down the size.
  
  <<Anchor(ubuntu_ec2_hangs)>>
+ <<Anchor(ubuntu_hangs)>>
  
- == I'm using Ubuntu on EC2 with JNA, and holy crap weird things keep hanging and stalling
and blocking and printing scary tracebacks in dmesg! ==
+ == I'm using Ubuntu with JNA, and holy crap weird things keep hanging and stalling and blocking
and printing scary tracebacks in dmesg! ==
  
  We have come across several different, but similar, sets of symptoms that might match what
you're seeing. They might all have the same root cause; it's not clear. One common piece is
messages like this in dmesg:
  
@@ -488, +489 @@

  "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
  }}}
  
- It does not seem that anyone has had the time to track this down to the real root cause,
but it does seem that upgrading the linux-image-virtual package and rebooting your instances
fixes it. There is likely some bug in several of the virtual/xen kernel builds distributed
by Ubuntu which is fixed in later versions. Versions of linux-image-*-virtual which are known
not to have this problem include:
+ It does not seem that anyone has had the time to track this down to the real root cause,
but it does seem that upgrading the linux-image package and rebooting your instances fixes
it. There is likely some bug in several of the kernel builds distributed by Ubuntu which is
fixed in later versions. Versions of linux-image-* which are known not to have this problem
include:
  
   * linux-image-2.6.38-10-virtual (2.6.38-10.46) (Ubuntu 11.04/Natty Narwhal)
   * linux-image-2.6.35-24-virtual (2.6.35-24.42) (Ubuntu 10.10/Maverick Meerkat)

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