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Hello everyone,

here I will briefly summarize an export update problem one will encounter
when using nfs-ganesha.

While working on a driver that relies on nfs-ganesha I have discovered that
it
is apparently impossible to provide interruption-free export updates. As of
version
2.3 which I am working with it is possible to add an export or to remove an
export without restarting the daemon, but it is not possible to modify an
existing
export. So in other words if you create an export you should define all
clients
before you actually export and use it, otherwise it will be impossible to
change
rules on the fly. One can come up with at least two ways to work around
this issue: either by removing, updating and re-adding an export, or by
creating multiple
exports (one per client) for an exported resource. Both ways have associated
problems: the first one interrupts clients already working with an export,
which might be a big problem if a client is doing heavy I/O, the second one
creates multiple exports associated with a single resource, which can
easily lead
to confusion. The second approach is used in current manila's ganesha
helper[1].
This issue seems to be raised now and then with nfs-ganesha team, most
recently in
[2], but apparently it will not  be addressed in the nearest future.

With kind regards,
Alexey.

[1]:
https://github.com/openstack/manila/blob/master/manila/share/drivers/ganesha/__init__.py
[2]: https://sourceforge.net/p/nfs-ganesha/mailman/message/35173839
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