Hi All, I've got a new issue (hopefully this one will be the last). I have a working Ceph (Octopus) cluster with a replicated pool (my-pool), an erasure-coded pool (my-pool-data), and an image (my-image) created - all *seems* to be working correctly. I also have the correct Keyring specified (ceph.client.my-id.keyring). ceph -s is reporting all healthy. The ec profile (my-ec-profile) was created with: ceph osd erasure-code-profile set my-ec-profile k=4 m=2 crush-failure-domain=host The replicated pool was created with: ceph osd pool create my-pool 100 100 replicated Followed by: rbd pool init my-pool The ec pool was created with: ceph osd pool create my-pool-data 100 100 erasure my-ec-profile --autoscale-mode=on Followed by: rbd pool init my-pool-data The image was created with: rbd create -s 1T --data-pool my-pool-data my-pool/my-image The Keyring was created with: ceph auth get-or-create client.my-id mon 'profile rbd' osd 'profile rbd pool=my-pool' mgr 'profile rbd pool=my-pool' -o /etc/ceph/ceph.client.my-id.keyring On a centos8 client machine I have installed ceph-common, placed the Keyring file into /etc/ceph/, and run the command: rbd device map my-pool/my-image --id my-id All *seems* AOK. However - and here's my issue - when I try to create a partition on /dev/rbd0 and/or try to mount it, the client reports: fdisk: cannot open /dev/rbd0: Input/output error  OR mount: /my-rbd-bloc-device: special device /dev/rbd0 does not exist (respectively). What am I doing wrong? Thanks in advance for the help Matthew J -- Peregrine IT Signature *Matthew J BLACK*   M.Inf.Tech.(Data Comms)   MBA   B.Sc.   MACS (Snr), CP, IP3P When you want it done /right/ ‒ the first time! Phone: +61 4 0411 0089 Email: matthew(a)peregrineit.net <mailto:matthew@peregrineit.net> Web: www.peregrineit.net <http://www.peregrineit.net> View Matthew J BLACK's profile on LinkedIn <http://au.linkedin.com/in/mjblack> This Email is intended only for the addressee.  Its use is limited to that intended by the author at the time and it is not to be distributed without the author’s consent.  You must not use or disclose the contents of this Email, or add the sender’s Email address to any database, list or mailing list unless you are expressly authorised to do so.  Unless otherwise stated, Peregrine I.T. Pty Ltd accepts no liability for the contents of this Email except where subsequently confirmed in writing.  The opinions expressed in this Email are those of the author and do not necessarily represent the views of Peregrine I.T. Pty Ltd.  This Email is confidential and may be subject to a claim of legal privilege. If you have received this Email in error, please notify the author and delete this message immediately.