[Lustre-discuss] Optimal stratgy for OST distribution

[Heckes, Frank]

Hi all,

sorry if this question has been answered before.

What is the optimal 'strategy' assigning OSTs to OSS nodes:

-a- Assign OST via round-robin to the OSS
-b- Assign in consecutive order (as long as the backend storage provides
    enought capacity for iops and bandwidth)
-c- Something 'in-between' the 'extremes' of -a- and -b-

E.g.:

-a-     OSS_1           OSS_2           OST_3
          |_              |_              |_
            OST_1           OST_2           OST_3
            OST_4           OST_5           OST_6
            OST_7           OST_8           OST_9

-b-     OSS_1           OSS_2           OST_3
          |_              |_              |_
            OST_1           OST_4           OST_7
            OST_2           OST_5           OST_8
            OST_3           OST_6           OST_9

I thought -a- would be best for task-local (each task write to own
file) and single file (all task write to single file) I/O since its like
a raid-0 approach used disk I/O (and SUN create our first FS this way).
Does someone made any systematic investigations which approach is best
or have some educated opinion?
Many thanks in advance.
BR

-Frank Heckes

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