Hi,
pNFS is a feature introduced as part of NFSv4.1 protocol to allow direct
client access to storage devices containing file data (in short parallel
I/O). Client request for the layouts of entire file or specific range.
On receiving the layout information, they shall directly contact the
server containing the data for the I/O.
In case of a cluster of (NFS)servers,
* Meta-data servers (MDS) are responsible to provide layouts of the
file and recall them in case of any change in the layout.
* Data servers (DS) contain the actual data and process the I/O.
For more information, kindly refer to [1].
Currently with NFS-Ganesha+GlusterFS, we support FILE_LAYOUTs but with
single MDS.
So
* to avoid single point of failure & be able to support multiple MDS and
* to recall the layout in case of cluster of (NFS)servers,
we need to store the layouts on the back-end filesystem(GlusterFS) and
recall them in case of any conflicting access which may change the file
layout.
Since it is on similar lines to storing and recalling lease state (with
slightly different semantics), we are planning to store and process them
as a special type of lease ('LAYOUT') in the lease xlator being worked
upon as part of [2].
More details are captured in the below spec [3] :
http://review.gluster.org/#/c/12367
Kindly review the same and provide your inputs/comments.
Thanks,
Soumya
[1] https://tools.ietf.org/rfc/rfc5661.txt (Section 12. Parallel NFS (pNFS))
[2] http://review.gluster.org/#/c/11980/
[3] http://review.gluster.org/#/c/12367
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