Eduardo,
We have confirmed that if file stuffing is turned off, servers to store the
data are allocated as you expect in a round robin fashion. If file stuffing
is turned on, then the order of servers is not guaranteed.
If your use case depends on round robin, you can turn off stuffing by
modifying the config file as shown below and restarting your servers.
<Filesystem>
...
FileStuffing no
...
</Filesystem>
Hope that helps!
Elaine
On Tue, Sep 6, 2016 at 5:49 PM, Becky Ligon <[email protected]> wrote:
> Eduardo:
>
> Looks like you have uncovered a bug. So far, we have found the problem as
> far back as 2.8.4. We are still investigating and will keep you posted.
>
> thanks!
> Becky Ligon
>
> On Tue, Sep 6, 2016 at 3:34 PM, Eduardo CAMILO Inacio <
> [email protected]> wrote:
>
>> Dear PVFS2 users,
>>
>> After performing some experiments on OrangeFS 2.8.8, I am a little
>> confused about the default distribution layout. Systems manual, change log,
>> and some published papers claim that it should be ROUND_ROBIN. By that, I
>> understand that a server is randomly chosen to store the first 64 KB of the
>> file, and the second 64 KB block would be stored in the next server
>> according to the order in the configuration file, and so on.
>>
>> In my experiments, what I am observing is more close to the behavior I
>> would expect with a RANDOM layout. For instance, when two out of four
>> servers are chosen to store objects from a file, independently if the
>> "user.pvfs2.num_dfiles" is set to 2 or if the file size is just 2x the
>> stripe size, it seems like the two servers are being chosen randomly.
>>
>> It is worth noting that no change was performed in the generated config
>> file; the number of data files is changed through setfattr commands before
>> experiments. POSIX requests are being generated using the IOR benchmark
>> v3.0.1 with MPICH 3.2, which, I am assuming, is not changing the layout of
>> the file system.
>>
>> Attached, you will find some output that illustrate the aforementioned
>> behavior.
>>
>> Any insight on this subject would be helpful.
>>
>> Best,
>> --
>> Eduardo Camilo Inacio
>>
>> _______________________________________________
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>> [email protected]
>> http://www.beowulf-underground.org/mailman/listinfo/pvfs2-users
>>
>>
>
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