Re: High CPU/Delay when Removing Layered Child RBD Image

Robert LeBlanc <robert@xxxxxxxxxxxxx> · Fri, 19 Dec 2014 11:20:02 -0700

Do you know if this value is not set if it uses 4MB or 4096 bytes?
Thanks,
Robert LeBlanc

On Thu, Dec 18, 2014 at 6:51 PM, Tyler Wilson <kupo@xxxxxxxxxxxxxxxx> wrote:Okay, this is rather unrelated to Ceph but I might as well mention how this is fixed. When using the Juno-Release OpenStack pages the 'rbd_store_chunk_size = 8' now sets it to 8192 bytes rather than 8192 kB (8MB) causing quite a bit more objects to be stored and deleted. Setting this to 8192 got me the expected object size of 8MB.

On Thu, Dec 18, 2014 at 6:22 PM, Tyler Wilson <kupo@xxxxxxxxxxxxxxxx> wrote:Hey All,
On a new Cent7 deployment with firefly I'm noticing a strange behavior when deleting RBD child disks. It appears upon deletion cpu usage on each OSD process raises to about 75% for 30+ seconds. On my previous deployments with CentOS 6.x and Ubuntu 12/14 this was never a problem.

Each RBD Disk is 4GB created with 'rbd clone images/136dd921-f6a2-432f-b4d6-e9902f71baa6@snap compute/test'

## Ubuntu12 3.11.0-18-generic with Ceph 0.80.7
root@node-1:~# date; rbd rm compute/test123; date
Fri Dec 19 01:09:31 UTC 2014
Removing image: 100% complete...done.
Fri Dec 19 01:09:31 UTC 2014

## Cent7 3.18.1-1.el7.elrepo.x86_64 with Ceph 0.80.7
[root@hvm003 ~]# date; rbd rm compute/test; date
Fri Dec 19 01:08:32 UTC 2014
Removing image: 100% complete...done.
Fri Dec 19 01:09:00 UTC 2014

root@cpl001 ~]# ceph -s
    cluster d033718a-2cb9-409e-b968-34370bd67bd0
     health HEALTH_OK
     monmap e1: 3 mons at {cpl001=10.0.0.1:6789/0,mng001=10.0.0.3:6789/0,net001=10.0.0.2:6789/0}, election epoch 10, quorum 0,1,2 cpl001,net001,mng001
     osdmap e84: 9 osds: 9 up, 9 in
      pgmap v618: 1792 pgs, 12 pools, 4148 MB data, 518 kobjects
            15106 MB used, 4257 GB / 4272 GB avail
                1792 active+clean

Any assistance would be appreciated.

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