Hey Chris, sorry for the late reply. On 01/27/2016 10:53 PM, Chris Murphy wrote: > I can't exactly reproduce this. I'm using +C qcow2 on Btrfs on one SSD > to back the drives in the VM. > > 2x btrfs raid1 with files totalling 5G consistently takes ~1 minute > [1] to balance (no filters) > > 4x btrfs raid6 with the same files *inconsistently* takes ~1m15s [2] > to balance (no filters) > iotop is all over the place, from 21MB/s writes to 527MB/s To be honest, 5G is not really 21T spread across 12 spindles with LOTS of data on them. On another box with 8x4TB spinning rust it's also very slow. > Do both of you get something like this: > [root@f23m ~]# dmesg | grep -i raid > [ 1.518682] raid6: sse2x1 gen() 4531 MB/s > [ 1.535663] raid6: sse2x1 xor() 3783 MB/s > [ 1.552683] raid6: sse2x2 gen() 10140 MB/s > [ 1.569658] raid6: sse2x2 xor() 7306 MB/s > [ 1.586673] raid6: sse2x4 gen() 11261 MB/s > [ 1.603683] raid6: sse2x4 xor() 7009 MB/s > [ 1.603685] raid6: using algorithm sse2x4 gen() 11261 MB/s > [ 1.603686] raid6: .... xor() 7009 MB/s, rmw enabled > [ 1.603687] raid6: using ssse3x2 recovery algorithm Yes: --- cut --- [ 4.704396] raid6: sse2x1 gen() 4288 MB/s [ 4.772401] raid6: sse2x1 xor() 4036 MB/s [ 4.840403] raid6: sse2x2 gen() 7629 MB/s [ 4.908405] raid6: sse2x2 xor() 6247 MB/s [ 4.976404] raid6: sse2x4 gen() 10221 MB/s [ 5.044397] raid6: sse2x4 xor() 7620 MB/s [ 5.044525] raid6: using algorithm sse2x4 gen() 10221 MB/s [ 5.044641] raid6: .... xor() 7620 MB/s, rmw enabled [ 5.044767] raid6: using ssse3x2 recovery algorithm --- cut --- Would some sort of stracing or profiling of the process help to narrow down where the time is currently spent and why the balancing is only running single-threaded? Regards Christian -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
