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Description of problem: Writes are slower when AIO is enabled: AIO write 4096 enabled: [root@gqac006 ~]# dd if=/dev/zero of=/gluster-mount/test.txt bs=1024k count=1000 conv=fdatasync 1000+0 records in 1000+0 records out 1048576000 bytes (1.0 GB) copied, 3.30806 s, 317 MB/s AIO disabled: [root@gqac006 ~]# dd if=/dev/zero of=/gluster-mount/test.txt bs=1024k count=1000 conv=fdatasync 1000+0 records in 1000+0 records out 1048576000 bytes (1.0 GB) copied, 2.78396 s, 377 MB/s Version-Release number of selected component (if applicable): [root@gqas001 ~]# rpm -q samba samba-4.2.4-13.el6rhs.x86_64 [root@gqas001 ~]# rpm -q glusterfs glusterfs-3.7.5-19.el6rhs.x86_64 How reproducible: Every way I have tested so far. Steps to Reproduce: 1. Enable aio write = 4096 in smb.conf 2. Run write benchmark with AIO enabled. Actual results: Writes are slower with AIO enabled. Expected results: Like reads, AIO writes will improve performance. Additional info:
AIO is not guaranteed to improve performance. AIO is an option we expect could slow down SOME workloads, and SMB1 single threaded workloads are among the ones I expect could get hit. Like your Linux workload. I'd also expect that any workload without significant parallelism, could be hurt. A multithreaded write windows workload MIGHT show a benefit. The workload you show, getting hurt, is no surprise. The reason it works for reads, is that almost all SMB clients do readahead, so we get a multithreaded workload for read, automatically. So, the write setting is likely more "tuning" oriented than the read one. But this is distinctly NOTABUG.