Erik Nieto wrote:
Hello Everybody:
I have some questions about the create system interface operation
in the 2.8.1 version of pvfs2.
In the earlier version (pvfs-2.7.1), the state machine:
1.- First create a space for the metafile.
2.- Next, create the datafiles in the indicated servers (following a
distribution).
3.- In the third step create the directory entry.
This steps are posted in the client side, but, searching in the new
create state machine, the creation of the datafiles is not included (on
the client side).
And my questions:
1.- Where is posted the datafiles create request, is on the metadata
servers?
2.- Are the metadata servers who post all the datafiles create requests?
3.- What method do you use for the creations of files in the new version
of pvfs2?
4.- Is there a place where I can analyze the new state machine operation?
5.- And last, is there comunication between servers (i.e. for the create
operation) in the new pvfs2 version?
Hi Erik,
The 2.8.0 release introduced some changes to how files are created in
PVFS. The metadata server handles allocating datafiles on behalf of the
client. Each metadata server preallocates a set of datafile handles in
the background to use for this purpose and refills the set as needed,
rather than requesting them on demand.
PVFS also "stuffs" files now. In our case that means that only a single
datafile is allocated and it is placed on the same server as the
metafile. The file is not un-stuffed until you write to a region of the
file that requires more datafiles to service.
There is some more information available in this paper if you are
interested:
http://www.mcs.anl.gov/uploads/cels/papers/P1571.pdf
-Phil
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