I used fs_usage to determine what was causing a periodic noise of disk usage and found that when bluetooth is enabled the OS has a flurry of activity to disk every few seconds.
What is this nonsense?
I'm using a mac mini (late 2014) and 10.11.6
11:51:01.947157 WrMeta[AT3] D=0x24837c88 B=0x2000 /dev/disk1 /Library/Preferences/com.apple.Bluetooth.plist 0.001919 W launchd.31845971
11:51:02.330797 WrData[A] D=0x24bce260 B=0x2000 /dev/disk1 /Library/Preferences/com.apple.Bluetooth.plist.oUfCvsH 0.000310 W cfprefsd.31841056
11:51:02.932974 WrData[AT2] D=0x24bce348 B=0x1000 /dev/disk1 y/Preferences/ByHost/com.apple.Bluetooth.090FDBDC-2499-5FDF-9C5A-FCF58BF57E69.plist.s7qR3Pj 0.000212 W cfprefsd.31841647
11:51:03.035805 WrData[A] D=0x24bce490 B=0x2000 /dev/disk1 /Library/Preferences/com.apple.Bluetooth.plist.6qKreYk 0.000391 W cfprefsd.31845345
11:51:03.040812 WrData[A] D=0x24bce4a0 B=0x2000 /dev/disk1 /Library/Preferences/com.apple.Bluetooth.plist.woGLECb 0.000216 W cfprefsd.31841056
11:51:03.045418 WrData[A] D=0x24bce4b0 B=0x2000 /dev/disk1 /Library/Preferences/com.apple.Bluetooth.plist.Sfp07t6 0.000207 W cfprefsd.31845345
11:51:03.049503 WrData[A] D=0x24bce510 B=0x2000 /dev/disk1 /Library/Preferences/com.apple.Bluetooth.plist.JkYIKtC 0.000249 W cfprefsd.31841055
11:51:07.425172 WrData[A] D=0x24bce7d8 B=0x2000 /dev/disk1 /Library/Preferences/com.apple.Bluetooth.plist.aDPHpWC 0.000259 W cfprefsd.31841055
11:51:07.609664 WrData[AT2] D=0x24bce7e8 B=0x1000 /dev/disk1 y/Preferences/ByHost/com.apple.Bluetooth.090FDBDC-2499-5FDF-9C5A-FCF58BF57E69.plist.9mlaRTL 0.000197 W cfprefsd.31841117
11:51:08.160607 WrData[A] D=0x24bce7f0 B=0x2000 /dev/disk1 /Library/Preferences/com.apple.Bluetooth.plist.fdVKH8T 0.000215 W cfprefsd.31841055
11:51:08.164127 WrData[A] D=0x24bce868 B=0x2000 /dev/disk1 /Library/Preferences/com.apple.Bluetooth.plist.g5SsBeG 0.000188 W cfprefsd.31841057
11:51:08.169654 WrData[A] D=0x24bce878 B=0x2000 /dev/disk1 /Library/Preferences/com.apple.Bluetooth.plist.nPIFbGw 0.000225 W cfprefsd.31841056
11:51:08.173485 WrData[A] D=0x24bce888 B=0x2000 /dev/disk1 /Library/Preferences/com.apple.Bluetooth.plist.9Q2yJkt 0.000207 W cfprefsd.31841057
11:51:08.763090 WrData[A] D=0x24bce898 B=0x2000 /dev/disk1 /Library/Preferences/com.apple.Bluetooth.plist.QQ8EZkK 0.000268 W cfprefsd.31841057
11:51:08.975709 WrData[AT2] D=0x24bce8a8 B=0x1000 /dev/disk1 y/Preferences/ByHost/com.apple.Bluetooth.090FDBDC-2499-5FDF-9C5A-FCF58BF57E69.plist.uP1JSJc 0.000201 W cfprefsd.31841647
11:51:09.497036 WrData[A] D=0x24bcea58 B=0x2000 /dev/disk1 /Library/Preferences/com.apple.Bluetooth.plist.tm1jLsF 0.000263 W cfprefsd.31846659
11:51:09.515961 WrData[A] D=0x24bceb68 B=0x2000 /dev/disk1 /Library/Preferences/com.apple.Bluetooth.plist.hvSQoa1 0.014639 W cfprefsd.31841055
11:51:09.521097 WrData[A] D=0x24bceba0 B=0x2000 /dev/disk1 /Library/Preferences/com.apple.Bluetooth.plist.sXpaR28 0.000271 W cfprefsd.31841055
11:51:09.524719 WrData[A] D=0x24bcebb0 B=0x2000 /dev/disk1 /Library/Preferences/com.apple.Bluetooth.plist.FNOEIIl 0.000231 W cfprefsd.31846659
11:51:17.673292 WrData[A] D=0x24bcecd0 B=0x2000 /dev/disk1 /Library/Preferences/com.apple.Bluetooth.plist.1ulwfcT 0.000298 W cfprefsd.31841055
11:51:17.924368 WrData[AT2] D=0x24bced10 B=0x1000 /dev/disk1 y/Preferences/ByHost/com.apple.Bluetooth.090FDBDC-2499-5FDF-9C5A-FCF58BF57E69.plist.XgYIeeT 0.000209 W cfprefsd.31844764
11:51:18.473022 WrData[A] D=0x24bced20 B=0x2000 /dev/disk1 /Library/Preferences/com.apple.Bluetooth.plist.HLj2lyQ 0.000268 W cfprefsd.31846914
11:51:18.495857 WrData[A] D=0x24bced30 B=0x2000 /dev/disk1 /Library/Preferences/com.apple.Bluetooth.plist.zUEJZAl 0.018898 W cfprefsd.31841056
11:51:18.500781 WrData[A] D=0x24bced40 B=0x2000 /dev/disk1 /Library/Preferences/com.apple.Bluetooth.plist.4ZAGxrB 0.000163 W cfprefsd.31846659
11:51:18.504387 WrData[A] D=0x24bced60 B=0x2000 /dev/disk1 /Library/Preferences/com.apple.Bluetooth.plist.xKPVuXa 0.000214 W cfprefsd.31846659
11:51:25.339113 WrData[A] D=0x24bced70 B=0x2000 /dev/disk1 /Library/Preferences/com.apple.Bluetooth.plist.Nt20EAb 0.000263 W cfprefsd.31847057
11:51:25.530800 WrData[AT2] D=0x24bced80 B=0x1000 /dev/disk1 y/Preferences/ByHost/com.apple.Bluetooth.090FDBDC-2499-5FDF-9C5A-FCF58BF57E69.plist.FyYzKdn 0.000186 W cfprefsd.31847065
11:51:26.061932 WrData[A] D=0x24bcee30 B=0x2000 /dev/disk1 /Library/Preferences/com.apple.Bluetooth.plist.J99PoWM 0.000235 W cfprefsd.31847061
11:51:26.066184 WrData[A] D=0x24bcee40 B=0x2000 /dev/disk1 /Library/Preferences/com.apple.Bluetooth.plist.dV4WC0q 0.000221 W cfprefsd.31847057
11:51:26.070935 WrData[A] D=0x24bcee90 B=0x2000 /dev/disk1 /Library/Preferences/com.apple.Bluetooth.plist.jAEcmZ6 0.000223 W cfprefsd.31847062
11:51:26.074204 WrData[A] D=0x24bceea8 B=0x2000 /dev/disk1 /Library/Preferences/com.apple.Bluetooth.plist.liFZDuf 0.000222 W cfprefsd.31847057
11:51:26.632362 WrData[A] D=0x24bceeb8 B=0x2000 /dev/disk1 /Library/Preferences/com.apple.Bluetooth.plist.AtWwZpl 0.000292 W cfprefsd.31847058
11:51:26.902602 WrData[AT2] D=0x24bceec8 B=0x1000 /dev/disk1 y/Preferences/ByHost/com.apple.Bluetooth.090FDBDC-2499-5FDF-9C5A-FCF58BF57E69.plist.uxkROL3 0.000258 W cfprefsd.31847127
11:51:27.347983 WrData[A] D=0x24bcf078 B=0x2000 /dev/disk1 /Library/Preferences/com.apple.Bluetooth.plist.7VfqyZv 0.000228 W cfprefsd.31847058
11:51:27.352236 WrData[A] D=0x24bcf0e8 B=0x2000 /dev/disk1 /Library/Preferences/com.apple.Bluetooth.plist.79XiqpH 0.000246 W cfprefsd.31847062
11:51:27.357569 WrData[A] D=0x24bcf110 B=0x2000 /dev/disk1 /Library/Preferences/com.apple.Bluetooth.plist.EwcgAdU 0.000191 W cfprefsd.31847059
11:51:27.361037 WrData[A] D=0x24bcf120 B=0x2000 /dev/disk1 /Library/Preferences/com.apple.Bluetooth.plist.HO2UImd 0.000179 W cfprefsd.31847062
11:51:31.741114 WrData[A] D=0x24bcf170 B=0x2000 /dev/disk1 /Library/Preferences/com.apple.Bluetooth.plist.WcpIw4Z 0.000256 W cfprefsd.31847057
