[Openstack-operators] Ceph crashes with larger clusters and denser hardware

Warren Wang warren at wangspeed.com
Thu Aug 28 21:20:29 UTC 2014

For me, it happened on .80.5, but is relevant to any version. Here is the




On Thu, Aug 28, 2014 at 4:51 PM, Fischer, Matt <matthew.fischer at twcable.com>

>  What version of ceph was this seen on?
>   From: Warren Wang <warren at wangspeed.com>
> Date: Thursday, August 28, 2014 10:38 AM
> To: "openstack-operators at lists.openstack.org" <
> openstack-operators at lists.openstack.org>
> Subject: [Openstack-operators] Ceph crashes with larger clusters and
> denser hardware
>  One of my colleagues here at Comcast just returned from the Operators
> Summit and mentioned that multiple folks experienced Ceph instability with
> larger clusters. I wanted to send out a note and save headache for some
> folks.
>  If you up the number of threads per OSD, there are situations where many
> threads could be quickly spawned. You must up the max number of PIDs
> available to the OS, otherwise you essentially get fork bombed. Every
> single Ceph process with crash, and you might see a message in your shell
> about "Cannot allocate memory".
> In your sysctl.conf:
> # For Ceph
> kernel.pid_max=4194303
>  Then run "sysctl -p". In 5 days on a lab Ceph box, we have mowed through
> nearly 2 million PIDs. There's a tracker about this to add it to the
> ceph.com docs.
> Warren
>  @comcastwarren
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