TL;DR
HP Microserver Gen 8 with B120i Smart Array (not external Smart Array P220i/P222/P420 Controller) has low i/o performance in esxi with driver scsi-hpvsa with version later than scsi-hpvsa-5.5.0-88OEM.550.0.0.1331820 have performance issues
Download scsi-hpvsa-5.5.0-88OEM.550.0.0.1331820.x86_64.vib
1 Remove the existing scsi-hpvsa_5.5.0.102-1O driver (via SSH) (enable maintenance mode first)
esxcli software vib remove -n scsi-hpvsa -f
2 Install the scsi-hpvsa-5.5.0-88 downgraded driver
esxcli software vib install -v /vmfs/volumes/datastore1/scsi-hpvsa-5.5.0-88OEM.550.0.0.1331820.x86_64.vib
3 If you have ESXi 6.5 and newer
disable ESXi vmc_ahci module (if not completed, ahci is used by default. eg array is not initialised via hpvsa and ahci initialises disks as 4 separate physical disks)
In ESXi 6.5 VMware using new AHCI-driver (vmw_ahci) and in ESXi 6 used hpvsa driver
esxcli system module set --enabled=false --module=vmw_ahci
4 reboot host
5 (optional) check write speed
# cd /vmfs/volumes/datastore1
# time dd if=/dev/zero of=tempfile bs=8k count=100000; rm -f tempfile
100000+0 records in
100000+0 records out
real 1m 47.34s (see this)
user 0m 3.81s