Hello, The direct writes are problematic on both writes and rewrites. Rewrites alone are another issue we have noticed. Since indirect (direct=0) workloads are fine, it seems that the easiest solution could be to force indirect IO operations for all workloads. However we didn't find such possibility.
-- S přáním pěkného dne / Best regards Mgr. Peter Hruška IT specialista M Computers s.r.o. Úlehlova 3100/10, 628 00 Brno-Líšeň (mapa<https://mapy.cz/s/gafufehufe>) T:+420 515 538 136 E: [email protected]<mailto:[email protected]> www.mcomputers.cz<http://www.mcomputers.cz/> www.lenovoshop.cz<http://www.lenovoshop.cz/> [cid:[email protected]] On Tue, 2024-03-12 at 09:59 +0100, Zdenek Salvet wrote: EXTERNÍ ODESÍLATEL On Mon, Mar 11, 2024 at 01:21:32PM +0000, Peter Hruška wrote: We encountered a problem with performance of writes on GPFS when the application uses direct io access. To simulate the issue it is enough to run fio with option direct=1. The performance drop is quite dramatic - 250 MiB/s vs. 2955 MiB/s. We've tried to instruct GPFS to ignore direct IO by using "disableDIO=yes". The directive didn't have any effect. Is there any possibility how to achieve that GPFS would ignore direct IO requests and use caching for everything? Hello, did you use pre-allocated file(s) (was it re-write) ? libaio traffic is not really asynchronous with respect to necessary metadata operations (allocating new space and writing allocation structures to disk) in most Linux filesystems and I guess this case is not heavily optimized in GPFS either (dioSmallSeqWriteBatching feature may help a little but it targets different scenario I think). Best regards, Zdenek Salvet [email protected]<mailto:[email protected]> Institute of Computer Science of Masaryk University, Brno, Czech Republic and CESNET, z.s.p.o., Prague, Czech Republic Phone: ++420-549 49 6534 Fax: ++420-541 212 747 ---------------------------------------------------------------------------- Teamwork is essential -- it allows you to blame someone else. _______________________________________________ gpfsug-discuss mailing list gpfsug-discuss at gpfsug.org http://gpfsug.org/mailman/listinfo/gpfsug-discuss_gpfsug.org
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