Hi Thoralf, On 26.02.20 15:35, thoralf schulze wrote:

recently, we've come across a lot of advice to only use replicated rados pools as default- (ie: root-) data pools for cephfs¹.

It should be possible to use an EC pool for CephFS data: https://docs.ceph.com/docs/master/cephfs/createfs/#using-erasure-coded-pools...

unfortunately, we either skipped or blatantly ignored this advice while creating our cephfs, so our default data pool is an erasure coded one with k=2 and m=4, which _should_ be fine availability-wise. could anyone elaborate on the impacts regarding the performance of the whole setup?

Apart from the CephFS issue I think EC pools should always have k >= m as m is the parity part.

if a migration to a replicated pool is recommend: would a simple ceph osd pool set $default_data crush_rule $something_replicated

suffice, or would you recommend a more elaborated approach, something along the lines of taking the cephfs down, copy contents of default_pool to default_new, rename default_new default_pool, taking the cephfs up again?

You can only migrate by rsync'ing the data to a complete new CephFS. There is no inplace migration possible. You also cannot convert a pool from EC to replicated or vice versa. Regards -- Robert Sander Heinlein Support GmbH Schwedter Str. 8/9b, 10119 Berlin https://www.heinlein-support.de Tel: 030 / 405051-43 Fax: 030 / 405051-19 Amtsgericht Berlin-Charlottenburg - HRB 93818 B Geschäftsführer: Peer Heinlein - Sitz: Berlin