Ceph map时报错：“rbd: sysfs write failed”

Ceph map时报错：“rbd: sysfs write failed”

报错内容如下：

[[email protected] my-cluster]# rbd map kurt --pool rbd --id admin
rbd: sysfs write failed
RBD image feature set mismatch. You can disable features unsupported by the kernel with "rbd feature disable kurt object-map fast-diff deep-flatten".
In some cases useful info is found in syslog - try "dmesg | tail".
rbd: map failed: (6) No such device or address

系统环境：

OS:Centos 7.7，Ceph:14.2.5

[[email protected] my-cluster]# cat /etc/redhat-release 
CentOS Linux release 7.7.1908 (Core)
[[email protected] my-cluster]# ceph -v
ceph version 14.2.5 (ad5bd132e1492173c85fda2cc863152730b16a92) nautilus (stable)

原因分析：

出现这种错误的原因是OS kernel不支持块设备镜像的一些特性，导致映射失败。

[[email protected] my-cluster]# rbd info kurt
rbd image 'kurt':
        size 1 GiB in 256 objects
        order 22 (4 MiB objects)
        snapshot_count: 0
        id: 14aba61bbdf84
        block_name_prefix: rbd_data.14aba61bbdf84
        format: 2
        features: layering, exclusive-lock, object-map, fast-diff, deep-flatten
        op_features: 
        flags: 
        create_timestamp: Thu Dec 26 13:49:39 2019
        access_timestamp: Thu Dec 26 13:49:39 2019
        modify_timestamp: Thu Dec 26 13:49:39 2019

解决方法：

其实在报错信息里也非常明确的指出了解决方法。

RBD image feature set mismatch. You can disable features unsupported by the kernel with “rbd feature disable kurt object-map fast-diff deep-flatten”.

把 " "中间的那段rbd feature disable kurt object-map fast-diff deep-flatten复制出来并执行就可以了。

[[email protected] my-cluster]# rbd feature disable kurt object-map fast-diff deep-flatten
[[email protected] my-cluster]# rbd info kurt
rbd image 'kurt':
        size 1 GiB in 256 objects
        order 22 (4 MiB objects)
        snapshot_count: 0
        id: 14aba61bbdf84
        block_name_prefix: rbd_data.14aba61bbdf84
        format: 2
        features: layering, exclusive-lock
        op_features: 
        flags: 
        create_timestamp: Thu Dec 26 13:49:39 2019
        access_timestamp: Thu Dec 26 13:49:39 2019
        modify_timestamp: Thu Dec 26 13:49:39 2019

可以看到 features:下的object-map fast-diff deep-flatten都已经被禁用了。
再次map，OK搞定！

[[email protected] my-cluster]# rbd map kurt --pool rbd --id admin
/dev/rbd2