After installing 6.4.0-rc7a, My cache drive (ssd in the listing) was missing (more on that later) and in the syslog was this section.  Initially, on the Main page under the cache drive was an 'warning' about some non-zero data being found.  At that point , there was no listing in the GUI of the missing drive (sdd) either as being assigned as the cache drive or as an unassigned device. 

 

I started out to prepare this report (getting the section of the syslog, downloading the diagnostics file, etc)  and I went back to the Main Page and suddenly there was a 'Unassigned Devices' section/tab on the Main page and the missing drive was listed!  I stopped the array and assigned the the drive as the cache drive and restarted the array.  Everything appears to be working fine at this point.

 

Jul 28 07:13:41 Rose emhttpd: Device inventory:
Jul 28 07:13:41 Rose emhttpd: Hitachi_HDS721010CLA332_JP2911HD0Y80KC (sdg) 976762552
Jul 28 07:13:41 Rose emhttpd: WDC_WD30EFRX-68EUZN0_WD-WMC4N0K8P3JK (sdh) 2930266532
Jul 28 07:13:41 Rose emhttpd: WDC_WD3200AAJS-56M0A0_WD-WCAV2L226353 (sdd) 312571192
Jul 28 07:13:41 Rose emhttpd: Hitachi_HDS721010CLA332_JP6930HD15DEMF (sde) 976762552
Jul 28 07:13:41 Rose emhttpd: err: ckmbr: No medium found (123): open: /dev/sdb
Jul 28 07:13:41 Rose emhttpd: device /dev/sdb problem getting size
Jul 28 07:13:41 Rose emhttpd: Hitachi_HDS721010DLE630_MSK5235H2JJTTL (sdf) 976762552
Jul 28 07:13:41 Rose emhttpd: Hitachi_HDS721010CLA332_JP6930HD13JA2F (sdc) 976762552
Jul 28 07:13:41 Rose emhttpd: Generic-_USB3.0_CRW_-0_000000015140-0:0 (sda) 7639008
Jul 28 07:13:41 Rose kernel: mdcmd (1): import 0 sdh 2930266532 0 WDC_WD30EFRX-68EUZN0_WD-WMC4N0K8P3JK
Jul 28 07:13:41 Rose kernel: md: import disk0: (sdh) WDC_WD30EFRX-68EUZN0_WD-WMC4N0K8P3JK size: 2930266532 
Jul 28 07:13:41 Rose kernel: mdcmd (2): import 1 sdg 976762552 0 Hitachi_HDS721010CLA332_JP2911HD0Y80KC
Jul 28 07:13:41 Rose kernel: md: import disk1: (sdg) Hitachi_HDS721010CLA332_JP2911HD0Y80KC size: 976762552 
Jul 28 07:13:41 Rose kernel: mdcmd (3): import 2 sde 976762552 0 Hitachi_HDS721010CLA332_JP6930HD15DEMF
Jul 28 07:13:41 Rose kernel: md: import disk2: (sde) Hitachi_HDS721010CLA332_JP6930HD15DEMF size: 976762552 
Jul 28 07:13:41 Rose kernel: mdcmd (4): import 3 sdf 976762552 0 Hitachi_HDS721010DLE630_MSK5235H2JJTTL
Jul 28 07:13:41 Rose kernel: md: import disk3: (sdf) Hitachi_HDS721010DLE630_MSK5235H2JJTTL size: 976762552 
Jul 28 07:13:41 Rose kernel: mdcmd (5): import 4 sdc 976762552 0 Hitachi_HDS721010CLA332_JP6930HD13JA2F
Jul 28 07:13:41 Rose kernel: md: import disk4: (sdc) Hitachi_HDS721010CLA332_JP6930HD13JA2F size: 976762552 
Jul 28 07:13:41 Rose kernel: mdcmd (6): import 5
Jul 28 07:13:41 Rose kernel: mdcmd (7): import 6
Jul 28 07:13:41 Rose kernel: mdcmd (8): import 7
Jul 28 07:13:41 Rose kernel: mdcmd (9): import 8
Jul 28 07:13:41 Rose kernel: mdcmd (10): import 9
Jul 28 07:13:41 Rose kernel: mdcmd (11): import 10
Jul 28 07:13:41 Rose kernel: mdcmd (12): import 11
Jul 28 07:13:41 Rose kernel: mdcmd (13): import 12
Jul 28 07:13:41 Rose kernel: mdcmd (14): import 13
Jul 28 07:13:41 Rose kernel: mdcmd (15): import 14
Jul 28 07:13:41 Rose kernel: mdcmd (16): import 15
Jul 28 07:13:41 Rose kernel: mdcmd (17): import 16
Jul 28 07:13:41 Rose kernel: mdcmd (18): import 17
Jul 28 07:13:41 Rose kernel: mdcmd (19): import 18
Jul 28 07:13:41 Rose kernel: mdcmd (20): import 19
Jul 28 07:13:41 Rose kernel: mdcmd (21): import 20
Jul 28 07:13:41 Rose kernel: mdcmd (22): import 21
Jul 28 07:13:41 Rose kernel: mdcmd (23): import 22
Jul 28 07:13:41 Rose kernel: mdcmd (24): import 23
Jul 28 07:13:41 Rose kernel: mdcmd (25): import 24
Jul 28 07:13:41 Rose kernel: mdcmd (26): import 25
Jul 28 07:13:41 Rose kernel: mdcmd (27): import 26
Jul 28 07:13:41 Rose kernel: mdcmd (28): import 27
Jul 28 07:13:41 Rose kernel: mdcmd (29): import 28
Jul 28 07:13:41 Rose kernel: mdcmd (30): import 29
Jul 28 07:13:41 Rose kernel: md: import_slot: 29 empty
Jul 28 07:13:41 Rose emhttpd: import 30 cache device: no device

Now, all of this is virtually identical to the issue that I was having with 6.4.0-rc6 which is described here:
       https://forums.lime-technology.com/topic/58994-ver640rc6-cache-drive-not-found-and-started/

The difference at this point is that with 6.4.0-rc6, the missing cache drive always showed up as a unassigned device and not completely missing from the GUI.

rose-diagnostics-20170728-0722.zip

Edited July 28, 20178 yr by Frank1940

In the interest of completeness, here is the diagnostics file from after the detection of the drive I use for the cache drive as an unassigned device and its subsequent reassignment as the cache drive.

rose-diagnostics-20170728-0853.zip

After I read @Pauven's comment in the release thread for 6.4.0-rc7a, I decided to try an reboot.  This time the cache drive was properly assigned when the server came back up.  So, at this point, this appears to be an non-issue. 

 

I am not sure what the problem was unless the super.dat file was scrambled as I had the warning about some issue with 'bad' data in the cache section/tab. (Sorry that it got lost along the way as I was doing a fair amount of copying-and-pasting and lost track that I had not pasted that warning somewhat before I did the next copy...) 

Edited July 28, 20178 yr by Frank1940