Smart Array "Mixed mode" makes drive letter change UN-CONTROLLABLE AND UN-WANTED

[DC-HK]

System configuration:

• Proliant ML350 Gen10 with Smart Array P816i-a
• HDD: 8TB SAS
• OS: CentOS 7.4

Symtoms:

Unwanted and un-modifiable behaviour of Smart Array "Mixed mode". Drive letter for OS system drive (Logical drive created by RAID setup) will change when new unassigned drives are inserted into the system.

It seems to be related to the "Mixed mode" behaviour. Unfortunately, according to the "HPE Smart Array SR Gen10 Configuration Guide" (part no. 882375-002), the mixed mode of Port settings is "cannot be disabled".

Here is self explained terminal output log:

*** Power up with RAID 0 on hdd 1

[ict@server002 ~]$ ls -al /dev/sd*

brw-rw----. 1 root disk 8, 0 May 21 15:52 /dev/sda

brw-rw----. 1 root disk 8, 1 May 21 15:52 /dev/sda1

brw-rw----. 1 root disk 8, 2 May 21 15:52 /dev/sda2

brw-rw----. 1 root disk 8, 3 May 21 15:52 /dev/sda3

brw-rw----. 1 root disk 8, 16 May 21 15:52 /dev/sdb

[ict@server002 ~]$ echo "Insert hdd 2"

Insert hdd 2

[ict@server002 ~]$ ls -al /dev/sd*

brw-rw----. 1 root disk 8, 0 May 21 15:52 /dev/sda

brw-rw----. 1 root disk 8, 1 May 21 15:52 /dev/sda1

brw-rw----. 1 root disk 8, 2 May 21 15:52 /dev/sda2

brw-rw----. 1 root disk 8, 3 May 21 15:52 /dev/sda3

brw-rw----. 1 root disk 8, 16 May 21 15:52 /dev/sdb

brw-rw----. 1 root disk 8, 32 May 21 16:49 /dev/sdc

[ict@server002 ~]$ echo "Insert hdd 3"

Insert hdd 3

[ict@server002 ~]$ ls -al /dev/sd*

brw-rw----. 1 root disk 8, 0 May 21 15:52 /dev/sda

brw-rw----. 1 root disk 8, 1 May 21 15:52 /dev/sda1

brw-rw----. 1 root disk 8, 2 May 21 15:52 /dev/sda2

brw-rw----. 1 root disk 8, 3 May 21 15:52 /dev/sda3

brw-rw----. 1 root disk 8, 16 May 21 15:52 /dev/sdb

brw-rw----. 1 root disk 8, 32 May 21 16:49 /dev/sdc

brw-rw----. 1 root disk 8, 48 May 21 16:56 /dev/sdd

[ict@server002 ~]$ echo "Insert hdd 4"

Insert hdd 4

[ict@server002 ~]$ ls -al /dev/sd*

brw-rw----. 1 root disk 8, 0 May 21 15:52 /dev/sda

brw-rw----. 1 root disk 8, 1 May 21 15:52 /dev/sda1

brw-rw----. 1 root disk 8, 2 May 21 15:52 /dev/sda2

brw-rw----. 1 root disk 8, 3 May 21 15:52 /dev/sda3

brw-rw----. 1 root disk 8, 16 May 21 15:52 /dev/sdb

brw-rw----. 1 root disk 8, 32 May 21 16:49 /dev/sdc

brw-rw----. 1 root disk 8, 48 May 21 16:56 /dev/sdd

brw-rw----. 1 root disk 8, 64 May 21 16:56 /dev/sde

[ict@server002 ~]$

*** Power off

2018-May-23 Power up with all drive inserted already

[ict@server002 ~]$ ls -al /dev/sd*

brw-rw----. 1 root disk 8, 0 May 23 10:43 /dev/sda

brw-rw----. 1 root disk 8, 16 May 23 10:43 /dev/sdb

brw-rw----. 1 root disk 8, 32 May 23 10:43 /dev/sdc

brw-rw----. 1 root disk 8, 48 May 23 10:43 /dev/sdd

brw-rw----. 1 root disk 8, 49 May 23 10:43 /dev/sdd1

brw-rw----. 1 root disk 8, 50 May 23 10:43 /dev/sdd2

brw-rw----. 1 root disk 8, 51 May 23 10:43 /dev/sdd3

brw-rw----. 1 root disk 8, 64 May 23 10:43 /dev/sde

[ict@server002 ~]$

*** Power off

2018-May-24 Power up with 4th drive unpluged

[ict@server002 ~]$ ls -al /dev/sd*

brw-rw----. 1 root disk 8, 0 May 24 08:37 /dev/sda

brw-rw----. 1 root disk 8, 16 May 24 08:37 /dev/sdb

brw-rw----. 1 root disk 8, 32 May 24 08:37 /dev/sdc

brw-rw----. 1 root disk 8, 33 May 24 08:37 /dev/sdc1

brw-rw----. 1 root disk 8, 34 May 24 08:37 /dev/sdc2

brw-rw----. 1 root disk 8, 35 May 24 08:37 /dev/sdc3

brw-rw----. 1 root disk 8, 48 May 24 08:37 /dev/sdd