So, I have a next problem... I had an array with 4 disks: 2TB WD RED - parity disk, 2TB WD RED - data disk1, 2TB WD RED - data disk2 and 500GB Samsung - data disk3. I've decided to use the smallest disk as the cache disk, so I copied everything from it to another disk, stopped the array, unassigned from the array disk3 and assign it as the cache disk. Next I've hit the New Config from Tools and pointed the disk which was a parity disk as the parity, data1 as disk1 and data2 as disk2. So now I have three WD RED 2TB disks in the array but I can't start the array because I've got a massage that... "Disk in parity slot is not biggest" Any ideas how to deal with this problem?

Tools - Diagnostics. Post complete zip.

Diagnostics file attached.

statekmatka-diagnostics-20151020-2005.zip

Before New Config

Oct 20 11:03:00 StatekMatka kernel: mdcmd (1): import 0 8,64 1953514552 WDC_WD20EFRX-68EUZN0_WD-WMC4M1458649
Oct 20 11:03:00 StatekMatka kernel: md: import disk0: [8,64] (sde) WDC_WD20EFRX-68EUZN0_WD-WMC4M1458649 size: 1953514552
Oct 20 11:03:00 StatekMatka kernel: mdcmd (2): import 1 8,16 1953513492 WDC_WD20EFRX-68EUZN0_WD-WCC4M1116932
Oct 20 11:03:00 StatekMatka kernel: md: import disk1: [8,16] (sdb) WDC_WD20EFRX-68EUZN0_WD-WCC4M1116932 size: 1953513492
Oct 20 11:03:00 StatekMatka kernel: mdcmd (3): import 2 0,0
Oct 20 11:03:00 StatekMatka kernel: md: disk2 removed
Oct 20 11:03:00 StatekMatka kernel: mdcmd (4): import 3 8,32 1953514552 WDC_WD20EFRX-68EUZN0_WD-WCC4M1UC4XAV
Oct 20 11:03:00 StatekMatka kernel: md: import disk3: [8,32] (sdc) WDC_WD20EFRX-68EUZN0_WD-WCC4M1UC4XAV size: 1953514552

After New Config

Oct 20 11:07:03 StatekMatka kernel: mdcmd (1): import 0 8,16 1953513492 WDC_WD20EFRX-68EUZN0_WD-WCC4M1116932
Oct 20 11:07:03 StatekMatka kernel: md: import disk0: [8,16] (sdb) WDC_WD20EFRX-68EUZN0_WD-WCC4M1116932 size: 1953513492
Oct 20 11:07:03 StatekMatka kernel: md: disk0 new disk
Oct 20 11:07:03 StatekMatka kernel: mdcmd (2): import 1 8,32 1953514552 WDC_WD20EFRX-68EUZN0_WD-WCC4M1UC4XAV
Oct 20 11:07:03 StatekMatka kernel: md: import disk1: [8,32] (sdc) WDC_WD20EFRX-68EUZN0_WD-WCC4M1UC4XAV size: 1953514552
Oct 20 11:07:03 StatekMatka kernel: md: disk1 new disk
Oct 20 11:07:03 StatekMatka kernel: mdcmd (3): import 2 8,64 1953514552 WDC_WD20EFRX-68EUZN0_WD-WMC4M1458649
Oct 20 11:07:03 StatekMatka kernel: md: import disk2: [8,64] (sde) WDC_WD20EFRX-68EUZN0_WD-WMC4M1458649 size: 1953514552
Oct 20 11:07:03 StatekMatka kernel: md: disk2 new disk

Lucky for you disk1 was a little smaller, because you assigned it to parity and it would have been overwritten.

And make very sure you don't assign disk3 to parity, or it will get overwritten. See the serial numbers in the Before portion of the log.

:-[

Thank you very much, trurl...