Re: bluestore disks reading as ATARI/AHDI partitions

From what I have been reading, it's actually quite easy because AHDI partitions are so easily/loosely defined. I suspect Ubuntu has the kernel built with this enabled to allow for users emulating Atari systems. See here for reference: https://bugs.launchpad.net/ubuntu/+source/util-linux/+bug/1531404/comments/… <https://bugs.launchpad.net/ubuntu/+source/util-linux/+bug/1531404/comments/12> I suspect that Ceph's Bluestore layout has a high probability of matching these loose AHDI partitions at least in some cases. It seems very good that Centos 7 isn't built with AHDI support. Blaine On Tue, 22 Jun 2021 at 16:53, Steven Ellis &lt;sellis(a)redhat.com <mailto:sellis@redhat.com>> wrote: I'm rather puzzled as to why a disk is showing AHDI partition layout. It isn't something that should happen on a modern disk On Wed, 23 Jun 2021 at 10:07, Blaine Gardner &lt;brgardne(a)redhat.com <mailto:brgardne@redhat.com>> wrote: Hi All, We have had a strange issue crop up in Rook, and I wanted to bring it up for discussion more widely since I think it has the potential to affect cephadm deployments as well as Rook. Here if you want to look through it: https://github.com/rook/rook/issues/7940#issuecomment-865005220 <https://github.com/rook/rook/issues/7940#issuecomment-865005220> In Rook, we list disks with `lsblk` to be provisioned. I'm not sure how ceph-volume does this internally or how cephadm does this. In Rook (especially with 500+GB SSDs for some reason), many users are starting to see unexpected partitions appear. One user finally found out that this is because the Ubuntu kernel they're using has support for ATARI (AHDI) partitions. The kernel detects these as partitions, but lsblk does not understand the ATARI type and thus sees them as empty partitions. (It's unclear to me yet if `blkid` is able to see the ATARI type.) In Rook, this is really only a problem for OSDs that are provisioned on nodes (not a downstream-supported use-case). On PVCs (our downstream use-case), we only run the detection/provisioning step once at first setup, and so I believe Rook's downstream isn't affected. When provisioning OSDs on nodes, disk detection and OSD provisioning both run each time we reconcile. I'm not sure if that is true for cephadm or not. Additionally, the upstream user reports that ATARI/AHDI disk support is disabled for Centos 7. I hope this means we don't have to worry about this with Centos 8 or any RHEL we ship, but it might be good to confirm this for the RHEL versions we ship to customers. I'll leave the discussion of Rook-specific ideas for me, Seb, and Travis, but here are the questions I have for what we might need to think about for Ceph more broadly: Do we need to check Centos/RHEL versions for ATARI/AHDI disk support? Do we need to communicate to Ceph users that their bluestore OSD disks might appear as ATARI partitions on their host systems? Do we need to modify ceph-volume to do anything special if it finds ATARI/AHDI partitions? Are there other considerations I'm missing? Thanks again! And feel free to chime in with questions if I haven't explained things very well. Blaine -- Steven Ellis TECHNICAL PORTFOLIO EVANGELIST - APAC <https://www.redhat.com> APAC SENIOR PRINCIPAL PRODUCT MANAGER - OPENSHIFT INFRA & DATA SERVICES Red Hat Asia Pacific - Auckland NZ <https://www.redhat.com> E: sellis(a)redhat.com <mailto:sellis@redhat.com> M: +64 21 321 673 <tel:+64-21-321673> @RedHat <https://twitter.com/redhat> Red Hat <https://www.linkedin.com/company/red-hat> Red Hat <https://www.facebook.com/RedHatInc> <https://red.ht/sig> <https://redhat.com/trusted>