This made me nervous but it's clearly a cronjob based on the messages log that happens every Sunday at about 4:22.
I actually can't find any evidence of it in cron.d cron.daily but it is there somewhere obviously.
What I don't get is why doesn't this cronjob do a datacheck like Ubuntu's cronscript does? When you unnecessarily rebuild the array you lose your redundancy during that point which makes your data extremely vulnerable.
*Update I did a grep of "mdadm" in etc but this wouldnt' have come up.
I found the following script is responsible for this "/etc/cron.weekly/99-raid-check". It gets its config from /etc/sysconfig/raidcheck
Jan 9 04:22:01 server05 kernel: md: syncing RAID array md1
Jan 9 04:22:01 server05 kernel: md: minimum _guaranteed_ reconstruction speed: 1000 KB/sec/disc.
Jan 9 04:22:01 server05 kernel: md: using maximum available idle IO bandwidth (but not more than 200000 KB/sec) for reconstruction.
Jan 9 04:22:01 server05 kernel: md: using 128k window, over a total of 29302464 blocks.
Jan 9 04:22:01 server05 kernel: md: delaying resync of md2 until md1 has finished resync (they share one or more physical units)
Jan 9 04:27:00 server05 kernel: md: md1: sync done.
Jan 9 04:27:00 server05 kernel: md: syncing RAID array md2
Jan 9 04:27:00 server05 kernel: md: minimum _guaranteed_ reconstruction speed: 1000 KB/sec/disc.
Jan 9 04:27:00 server05 kernel: md: using maximum available idle IO bandwidth (but not more than 200000 KB/sec) for reconstruction.
Jan 9 04:27:00 server05 kernel: md: using 128k window, over a total of 488287552 blocks.
Jan 9 06:30:18 server05 kernel: md: md2: sync done.
Jan 2 04:22:01 server05 kernel: md: syncing RAID array md1
Jan 2 04:22:01 server05 kernel: md: minimum _guaranteed_ reconstruction speed: 1000 KB/sec/disc.
Jan 2 04:22:01 server05 kernel: md: using maximum available idle IO bandwidth (but not more than 200000 KB/sec) for reconstruction.
Jan 2 04:22:01 server05 kernel: md: using 128k window, over a total of 29302464 blocks.
Jan 2 04:26:57 server05 kernel: md: md1: sync done.
Dec 26 04:22:01 server05 kernel: md: syncing RAID array md1
Dec 26 04:22:01 server05 kernel: md: minimum _guaranteed_ reconstruction speed: 1000 KB/sec/disc.
Dec 26 04:22:01 server05 kernel: md: using maximum available idle IO bandwidth (but not more than 200000 KB/sec) for reconstruction.
Dec 26 04:22:01 server05 kernel: md: using 128k window, over a total of 29302464 blocks.
Dec 26 04:26:44 server05 kernel: md: md1: sync done.
Dec 19 04:22:01 server05 kernel: md: syncing RAID array md1
Dec 19 04:22:01 server05 kernel: md: minimum _guaranteed_ reconstruction speed: 1000 KB/sec/disc.
Dec 19 04:22:01 server05 kernel: md: using maximum available idle IO bandwidth (but not more than 200000 KB/sec) for reconstruction.
Dec 19 04:22:01 server05 kernel: md: using 128k window, over a total of 29302464 blocks.
Dec 19 04:22:01 server05 kernel: md: delaying resync of md2 until md1 has finished resync (they share one or more physical units)
Dec 19 04:27:05 server05 kernel: md: md1: sync done.
Dec 19 04:27:05 server05 kernel: md: syncing RAID array md2
Dec 19 04:27:05 server05 kernel: md: minimum _guaranteed_ reconstruction speed: 1000 KB/sec/disc.
Dec 19 04:27:05 server05 kernel: md: using maximum available idle IO bandwidth (but not more than 200000 KB/sec) for reconstruction.
Dec 19 04:27:05 server05 kernel: md: using 128k window, over a total of 488287552 blocks.
Dec 19 06:28:14 server05 kernel: md: md2: sync done.
Dec 12 04:22:01 server05 kernel: md: syncing RAID array md1
Dec 12 04:22:01 server05 kernel: md: minimum _guaranteed_ reconstruction speed: 1000 KB/sec/disc.
Dec 12 04:22:01 server05 kernel: md: using maximum available idle IO bandwidth (but not more than 200000 KB/sec) for reconstruction.
Dec 12 04:22:01 server05 kernel: md: using 128k window, over a total of 29302464 blocks.
Dec 12 04:26:44 server05 kernel: md: md1: sync done.
mdadm, centos, resyncthis, cronjob, cron, doesn, datacheck, ubuntu, cronscript, unnecessarily, rebuild, array, redundancy, update, grep, quot, etc, wouldnt, weekly, raid, config, sysconfig, raidcheck, server, kernel, md, syncing, _guaranteed_, reconstruction, kb, disc, maximum, idle, io, bandwidth, delaying, resync, sync, dec,