Feature #8196
open
Document which features are supported by the kernel client
Added by Ilya Dryomov about 10 years ago.
Updated almost 10 years ago.
Description
Document which kernel supports what and the possible pitfalls, like
#8178 and a number of "feature set mismatch" threads on the mailing
lists.
While documenting limitations is important I think that would hardly be enough.
For instance even latest kernel clients lose connectivity to RBD devices as soon as erasure pool is created (missing feature 4000000000). OK, erasure pools are not supported by kernel client but kernel client loses connectivity to FS as well.
One could use ceph-fuse instead but the latter makes it impossible to use `cephfs` utility which can only work through kernel client.
So merely creating erasure pool makes it impossible to manage multi-pool file system with `cephfs` as well as to access file system and RBD devices on replicated pools using kernel client. IMHO those limitations are too serious.
As Ilya mentioned in #8178:
The problem is that erasure compat flag is currently cluster-wide.
Perhaps at very least we should avoid blocking clients who don't use erasure pools directly.
Please create TODO bugs for all required features (if appropriate):
- `cephfs` fuse-client support
- limit erasure compatibility scope
- erasure support in kernel client
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