On Thu, Mar 2, 2017 at 1:06 AM, Sage Weil <sage@xxxxxxxxxxxx> wrote:
> On Thu, 2 Mar 2017, Xiaoxi Chen wrote:
>> >Still applies. Just create a Round Robin DNS record. The clients will
>> obtain a new monmap while they are connected to the cluster.
>> It works to some extent, but causing issue for "mount -a". We have such
>> deployment nowaday, a GTM(kinds of dns) record created with all MDS ips and
>> it works fine in terms of failover/ mount.
>>
>> But, user usually automation such mount by fstab and even, "mount -a " are
>> periodically called. With such DNS approach above, they will get mount point
>> busy message every time. Just due to mount.ceph resolve the DNS name to
>> another IP, and kernel client was feeling like you are trying to attach
>> another fs...
>
> The kernel client is (should be!) smart enough to tell that it is the same
> mount point and will share the superblock. If you see a problem here it's
> a bug.
I think -EBUSY actually points out that the sharing code is working.
The DNS name in fstab doesn't match the IPs it resolves to, so "mount
-a" attempts to mount. The kernel client tells that it's the same fs
and returns the existing super to the VFS. The VFS refuses the same
super on the same mount point...
We should look into enabling the in-kernel DNS resolver.
Thanks,
Ilya
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