Ubuntu Server on DL20Gen10 with P408i-a(RAID1): slow boot

[RobZ2]

I installed Ubuntu 20.04 on my DL20 Gen10. All seems to work, but booting takes a long time. The following spot in dmseg seems to be the culprit (going from  3.662367 to 123.389845)

Not sure why here it mentions RAID6, because the installed P408i-a is setup as RAID1. It seems that two scsi devices are involved. What is it doing for 2 minutes? Also on the console there is an extra message (not logged in dmseg) generated during these 2 minutes:
Begin: Loading essential drivers … [. 123.389845] raid6: avx2x4.   Gen(). 31519 MB/s

So how can I get Ubuntu kernel to do the right thing here? (related: what is difference between 6:1:0:0:and 6:2:0:0:? Wrong setup? Do I need to disable (hard- or software) something?)

Thanks! 

Relevant part of dmseg:

[ 3.481486] kernel: igb 0000:02:00.1 eno2: renamed from eth1
[ 3.494011] kernel: igb 0000:02:00.0 eno1: renamed from eth0
[ 3.505845] kernel: Console: switching to colour frame buffer device 210x65
[ 3.507544] kernel: mgag200 0000:01:00.1: fb0: mgag200drmfb frame buffer device
[ 3.603719] kernel: ata4: SATA link down (SStatus 0 SControl 300)
[ 3.605706] kernel: ata6: SATA link down (SStatus 0 SControl 300)
[ 3.605826] kernel: [drm] Initialized mgag200 1.0.0 20110418 for 0000:01:00.1 on minor 0
[ 3.606457] kernel: ata3: SATA link down (SStatus 0 SControl 300)
[ 3.607366] kernel: ata2: SATA link down (SStatus 0 SControl 300)
[ 3.608189] kernel: ata5: SATA link down (SStatus 0 SControl 300)
[ 3.608574] kernel: ata1: SATA link down (SStatus 0 SControl 300)
[ 3.610130] kernel: smartpqi 0000:04:00.0: Online Firmware Activation enabled
[ 3.610148] kernel: smartpqi 0000:04:00.0: Serial Management Protocol enabled
[ 3.610159] kernel: smartpqi 0000:04:00.0: New Soft Reset Handshake enabled
[ 3.610177] kernel: smartpqi 0000:04:00.0: RAID IU Timeout enabled
[ 3.610186] kernel: smartpqi 0000:04:00.0: TMF IU Timeout enabled
[ 3.612778] kernel: scsi host6: smartpqi
[ 3.621900] kernel: smartpqi 0000:04:00.0: added 6:0:-:- 51402ec01632c338 Enclosure HPE Smart Adapter AIO-
[ 3.625534] kernel: scsi 6:0:0:0: Enclosure HPE Smart Adapter 3.53 PQ: 0 ANSI: 5
[ 3.626896] kernel: scsi 6:0:0:0: Attached scsi generic sg0 type 13
[ 3.627548] kernel: smartpqi 0000:04:00.0: added 6:1:0:0 4000000000000000 Direct-Access HPE LOGICAL VOLUME SSDSmartPathCap+ En+ RAID-1(1+0)
[ 3.629174] kernel: scsi 6:1:0:0: Direct-Access HPE LOGICAL VOLUME 3.53 PQ: 0 ANSI: 5
[ 3.630442] kernel: sd 6:1:0:0: Attached scsi generic sg1 type 0
[ 3.630863] kernel: smartpqi 0000:04:00.0: added 6:2:0:0 0000000000000000 RAID HPE P408i-a SR Gen10
[ 3.632169] kernel: sd 6:1:0:0: [sda] 3125562032 512-byte logical blocks: (1.60 TB/1.46 TiB)
[ 3.632185] kernel: sd 6:1:0:0: [sda] 4096-byte physical blocks
[ 3.633229] kernel: scsi 6:2:0:0: RAID HPE P408i-a SR Gen10 3.53 PQ: 0 ANSI: 5
[ 3.633697] kernel: scsi 6:2:0:0: Attached scsi generic sg2 type 12
[ 3.635305] kernel: sd 6:1:0:0: [sda] Write Protect is off
[ 3.635327] kernel: sd 6:1:0:0: [sda] Mode Sense: 73 00 00 08
[ 3.635461] kernel: sd 6:1:0:0: [sda] Write cache: disabled, read cache: disabled, doesn't support DPO or FUA
[ 3.635671] kernel: sd 6:1:0:0: [sda] Optimal transfer size 262144 bytes
[ 3.638517] kernel: sda: sda1 sda2 sda3
[ 3.639311] kernel: ses 6:0:0:0: Attached Enclosure device
[ 3.662367] kernel: sd 6:1:0:0: [sda] Attached SCSI disk
[ 123.389845] kernel: raid6: avx2x4 gen() 31519 MB/s
[ 123.437821] kernel: raid6: avx2x4 xor() 18883 MB/s
[ 123.485862] kernel: raid6: avx2x2 gen() 26645 MB/s
[ 123.533846] kernel: raid6: avx2x2 xor() 24620 MB/s
[ 123.581847] kernel: raid6: avx2x1 gen() 20597 MB/s
[ 123.629822] kernel: raid6: avx2x1 xor() 22287 MB/s
[ 123.677851] kernel: raid6: sse2x4 gen() 11904 MB/s
[ 123.725858] kernel: raid6: sse2x4 xor() 7295 MB/s
[ 123.773868] kernel: raid6: sse2x2 gen() 10275 MB/s
[ 123.821843] kernel: raid6: sse2x2 xor() 10749 MB/s
[ 123.869854] kernel: raid6: sse2x1 gen() 9156 MB/s
[ 123.917855] kernel: raid6: sse2x1 xor() 8156 MB/s
[ 123.918581] kernel: raid6: using algorithm avx2x4 gen() 31519 MB/s
[ 123.919184] kernel: raid6: .... xor() 18883 MB/s, rmw enabled
[ 123.919784] kernel: raid6: using avx2x2 recovery algorithm
[ 123.921653] kernel: xor: automatically using best checksumming function avx
[ 123.924056] kernel: async_tx: api initialized (async)
[ 124.122350] kernel: Btrfs loaded, crc32c=crc32c-intel
[ 124.195346] kernel: EXT4-fs (dm-0): mounted filesystem with ordered data mode. Opts: (null)
[ 132.769882] kernel: hpsa 0000:01:00.7: board not ready, timed out.
[ 132.894056] systemd[1]: Inserted module 'autofs4'
[ 133.038576] systemd[1]: systemd 245.4-4ubuntu3.13 running in system mode. (+PAM +AUDIT +SELINUX +IMA +APPARMOR +SMACK +SYSVINIT +UTMP +LIBCRYPTSETUP +GCRYPT +GNUTLS +ACL +XZ +LZ4 +SECCOMP +BLKID +ELFUTILS +KMOD +IDN2 -IDN +PCRE2 default-hierarchy=hybrid)
[ 133.057879] systemd[1]: Detected architecture x86-64.

EDIT: I have come to realize that Ubuntu 20.04LTS is incompatible with DL20gen10, probably due to the hardware raid (P408i-a). Now installed RHEL8.5 and total dmseg is 10 seconds