First of all, I apologise if this mail list is not intended for layman help, but this is what I am and I couldn't get an explanation elsewhere. My problem is that (as it seems) mdadm is touching HDD superblocks once per second, once at address 8 (sectors), next at address 16. Total traffic is kilobytes per second, writes only, no other detectable traffic. I have detailed the problem here: http://unix.stackexchange.com/questions/329477/ Shortened: kubuntu 16.10 4.8.0-30-generic #32, mdadm v3.4 2016-01-28 My configuration: 4 spinning platters (/dev/sd[cdef]) assembled into a raid5 array, then bcache set to cache (hopefully) everything (cache_mode = writeback, sequential_cutoff = 0). On top of bcache volume I have set up lvm. * iostat shows traffic on sd[cdef] and md0 * iotop shows no traffic * iosnoop shows COMM=[idle, md0_raid5, kworker] as processes working on the disk. Blocks reported are 8, 16 (data size a few KB) and 18446744073709500000 (data size 0). That last one must be some virtual thingie as the disks are nowhere near that large. * enabling block_dump shows md0_raid5 process writing to block 8 (1 sectors) and 16 (8 sectors) This touching is caused by any write into the array and goes on for quite a while after the write has been done (a couple of hours for 60GB of writes). When services actually work with the array, this becomes pretty much constant. What am I observing and is there any way of stopping it? Thanks, Jure -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
