Hello, I am benchmarking Btrfs and when benchmarking random writes with fio utility, I noticed following two things:
1) On first run when target file doesn't exist yet, perfromance is about 8000 IOPs. On second, and every other run, performance goes up to 70000 IOPs. Its massive difference. The target file is the one created during the first run. 2) There are windows during the test where IOPs drop to 0 and stay 0 about 10 seconds and then it goes back again, and after couple of seconds again to 0. This is reproducible 100% times. Can somobody shred some light on what's happening? Command: fio --randrepeat=1 --ioengine=libaio --direct=1 --gtod_reduce=1 --name=test9 --filename=test9 --bs=4k --iodepth=256 --size=10G --numjobs=1 --readwrite=randwrite Environment: CPU: dual socket: E5-2630 v2 RAM: 32 GB ram OS: Ubuntu server 14.10 Kernel: 3.19.0-031900rc2-generic btrfs tools: Btrfs v3.14.1 2x LSI 9300 HBAs - SAS3 12/Gbs 8x SSD Ultrastar SSD1600MM 400GB SAS3 12/Gbs Regards, Premek -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
