Hi, On 02/01/2018 10:43 AM, Konstantin
Shalygin wrote:
We have changed our similar setup to a device class based one. According to the documentation the device classes are implemented by 'shadow' crush tree. 'ceph osd crush tree --show-shadow' displays all tree including the device class specific ones. This allows the device class setup to be backwards compatible with older releases. We had a MASSIVE data movement upon changing the crush rules to device class based one. I'm not sure about the exact reasons, but I assume that the order of hosts in the crush tree has changed (hosts are ordered lexically now...), which resulted in about 80% of data being moved around. So be prepared for slow requests, and set the corresponding configuration values to reduce the backfill impact. Regards, Burkhard |
_______________________________________________ ceph-users mailing list ceph-users@xxxxxxxxxxxxxx http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com