Hi,
here my console log where you see that the OS is doing it or reacting on an inconsistance !
29.10.13 19:25:53.000 kernel[0]: hfs: unmount initiated on VIDEO_1TB on device disk6s3
29.10.13 19:25:54.040 Finder[2197]: CreateWithFileInfo failed to create URL with FSRef, falling back to blank icon.
29.10.13 19:25:54.040 Finder[2319]: CreateWithFileInfo failed to create URL with FSRef, falling back to blank icon.
29.10.13 19:25:54.113 iTunes[2492]: ApplePushService: APSConnection being used without a delegate queue
29.10.13 19:25:54.550 diskmanagementd[2497]: unmount blocked by dissenter PID=2492 (/Applications/iTunes.app/Contents/MacOS/iTunes) status=0x0000c010 log=unknown message=(null)
29.10.13 19:26:01.000 kernel[0]: hfs: Initializing the journal (joffset 0xe8e000 sz 0x2800000)...
29.10.13 19:26:01.000 kernel[0]: hfs: mounted MyBook on device disk3s2
29.10.13 19:26:01.272 mds[89]: (Normal) Volume: volume:0x7fa055055200 ********** Bootstrapped Creating a default store:3 SpotLoc:/Volumes/MyBook/.Spotlight-V100 SpotVerLoc:/Volumes/MyBook/.Spotlight-V100/Store-V1 occlude:0 /Volumes/MyBook
29.10.13 19:26:01.970 fseventsd[53]: could not open <</Volumes/MyBook/.fseventsd/fseventsd-uuid>> (No such file or directory)
29.10.13 19:26:01.974 fseventsd[53]: log dir: /Volumes/MyBook/.fseventsd getting new uuid: BCFCAADF-FF62-4141-ACB6-A044CAFBCF24
29.10.13 19:26:01.974 fseventsd[53]: disk logger: failed to open output file /Volumes/FATBOY500/.fseventsd/000000000f331e8e (No such file or directory). mount point /Volumes/FATBOY500/.fseventsd
29.10.13 19:26:01.974 fseventsd[53]: disk logger: failed to open output file /Volumes/FATBOY500/.fseventsd/000000000f331e8e (No such file or directory). mount point /Volumes/FATBOY500/.fseventsd
29.10.13 19:26:03.684 coreservicesd[37]: Received request to reset fmod watch. Latest received id is 23838845711203. Latest sent id is 23838845711203
29.10.13 19:26:03.684 coreservicesd[37]: Received request to reset fmod watch. Latest received id is 23838845711203. Latest sent id is 23838845711203
29.10.13 19:26:03.684 coreservicesd[37]: Received request to reset fmod watch. Latest received id is 23838845711203. Latest sent id is 23838845711203
29.10.13 19:26:03.684 coreservicesd[37]: Received request to reset fmod watch. Latest received id is 23838845711203. Latest sent id is 23838845711203
29.10.13 19:26:03.704 mds[89]: (Normal) Volume: volume:0x7fa051018800 ********** Bootstrapped Creating a default store:0 SpotLoc:(null) SpotVerLoc:(null) occlude:0 /private/var/tmp/MPWYVRPJ
29.10.13 19:26:04.000 kernel[0]: hfs: Initializing the journal (joffset 0x1d1c000 sz 0x5000000)...
29.10.13 19:26:04.000 kernel[0]: hfs: mounted MyBook on device disk6s2
29.10.13 19:26:04.250 mds[89]: (Normal) Volume: volume:0x7fa052833000 ********** Bootstrapped Creating a default store:3 SpotLoc:/Volumes/MyBook 1/.Spotlight-V100 SpotVerLoc:/Volumes/MyBook 1/.Spotlight-V100/Store-V1 occlude:0 /Volumes/MyBook 1
29.10.13 19:26:05.100 fseventsd[53]: could not open <</Volumes/MyBook 1/.fseventsd/fseventsd-uuid>> (No such file or directory)
29.10.13 19:26:05.100 fseventsd[53]: log dir: /Volumes/MyBook 1/.fseventsd getting new uuid: E90833D0-619E-4EF2-93DB-40923BF2DD88
29.10.13 19:26:05.299 mds[89]: (Normal) Volume: volume:0x7fa053916000 ********** Bootstrapped Creating a default store:0 SpotLoc:(null) SpotVerLoc:(null) occlude:0 /private/var/tmp/MPJZCCNA
29.10.13 19:26:09.000 kernel[0]: Sandbox: mdworker(2551) deny file-read-data /BILDER/iPhoto Merge/Contents/PkgInfo
29.10.13 19:26:09.000 kernel[0]: Sandbox: mdworker(2551) deny file-read-data /BILDER/iPhoto Merge/Contents/PkgInfo
29.10.13 19:26:09.000 kernel[0]: Sandbox: mdworker(2551) deny file-read-data /BILDER/iPhoto Merge/Contents/PkgInfo
29.10.13 19:26:09.000 kernel[0]: Sandbox: mdworker(2551) deny file-read-data /BILDER/iPhoto Merge/Contents/PkgInfo
29.10.13 19:26:09.000 kernel[0]: Sandbox: mdworker(2551) deny file-read-data /BILDER/iPhoto Merge/Contents/PkgInfo
29.10.13 19:26:11.654 mds[89]: (Normal) Volume: volume:0x7fa052946800 ********** Bootstrapped Creating a default store:3 SpotLoc:/Volumes/EFI/.Spotlight-V100 SpotVerLoc:/Volumes/EFI/.Spotlight-V100/Store-V1 occlude:0 /Volumes/EFI
29.10.13 19:26:11.798 fseventsd[53]: could not open <</Volumes/EFI/.fseventsd/fseventsd-uuid>> (No such file or directory)
29.10.13 19:26:11.798 fseventsd[53]: log dir: /Volumes/EFI/.fseventsd getting new uuid: 3EE2F1B9-AA28-4EFA-97CA-FDCADE328774
29.10.13 19:26:11.845 mds[89]: (Normal) Volume: volume:0x7fa055053e00 ********** Bootstrapped Creating a default store:3 SpotLoc:/Volumes/EFI 1/.Spotlight-V100 SpotVerLoc:/Volumes/EFI 1/.Spotlight-V100/Store-V1 occlude:0 /Volumes/EFI 1
29.10.13 19:26:12.044 fseventsd[53]: could not open <</Volumes/EFI 1/.fseventsd/fseventsd-uuid>> (No such file or directory)
VIDEO_1TB destroyed to Mybook and EFI
FATBOY500 destroyed to Mybook and EFI
and... AUDIO_1TB is still save due to iTunes was running at that time :-)
Remark: All are single disks, no RAID.
Thanks Apple