[Gluster-devel] Upcall state + Data Tiering

[Soumya Koduri]

Hi Dan/Joseph,

As part of upcall support on the server-side, we maintain certain state 
to notify clients of the cache-invalidation and recall-leaselk events.

We have certain known limitations with Rebalance and Self-Heal. Details 
in the below link -
http://www.gluster.org/community/documentation/index.php/Features/Upcall-infrastructure#Limitations

In case of Cache-invalidation,
upcall state is not migrated and once the rebalance is finished, the 
file is deleted and we may falsely notify the client that file is 
deleted when in reality it isn't.

In case of Lease-locks,
As the case with posix locks, we do not migrate lease-locks as well but 
will end-up recalling lease-lock.

Here rebalance is an admin driven job, but that is not the case with 
respect to Data tiering.

We would like to know when the files are moved from hot to cold tiers or 
vice-versa or rather when a file is considered to be migrated from cold 
to hot tier, where we see potential issues.
Is it the first fop which triggers it? and
where are the further fops processed - on hot tier or cold tier?

Please provide your inputs on the same. We may need to document the same 
or provide suggestions to the customers while deploying this solution.

Thanks,
Soumya