Actually, the MDS will still assign OST indices in round-robin order unless the free space is more than 20% imbalanced.
However, it will internally do an OSS-first ordering of the OSTs to ensure maximum spreading of load across the OSS nodes. For details see lustre/lov/lov_qos.c. Cheers, Andreas On 2011-03-31, at 5:06 AM, Kevin Van Maren <[email protected]> wrote: > It used to be that multi-stripe files were created with sequential OST > indexes. It also used to be that OST indexes were sequentially assigned > to newly-created files. > As Lustre now adds greater randomization, the strategy for assigning > OSTs to OSS nodes (and storage hardware, which often limits the > aggregate performance of multiple OSTs) is less important. > > While I have normally gone with "a", "b" can make it easier to remember > where OSTs are located, and also keep a uniform convention if the > storage system is later grown. > > Kevin > > > Heckes, Frank wrote: >> 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 >> >> ------------------------------------------------------------------------------------------------ >> ------------------------------------------------------------------------------------------------ >> Forschungszentrum Juelich GmbH >> 52425 Juelich >> Sitz der Gesellschaft: Juelich >> Eingetragen im Handelsregister des Amtsgerichts Dueren Nr. HR B 3498 >> Vorsitzender des Aufsichtsrats: MinDirig Dr. Karl Eugen Huthmacher >> Geschaeftsfuehrung: Prof. Dr. Achim Bachem (Vorsitzender), >> Dr. Ulrich Krafft (stellv. Vorsitzender), Prof. Dr.-Ing. Harald Bolt, >> Prof. Dr. Sebastian M. Schmidt >> ------------------------------------------------------------------------------------------------ >> ------------------------------------------------------------------------------------------------ >> >> Besuchen Sie uns auf unserem neuen Webauftritt unter www.fz-juelich.de >> _______________________________________________ >> Lustre-discuss mailing list >> [email protected] >> http://lists.lustre.org/mailman/listinfo/lustre-discuss >> > > _______________________________________________ > Lustre-discuss mailing list > [email protected] > http://lists.lustre.org/mailman/listinfo/lustre-discuss _______________________________________________ Lustre-discuss mailing list [email protected] http://lists.lustre.org/mailman/listinfo/lustre-discuss
