Oracle Database 12,18,19: Practices for using ASMLib with Multipath Devices (Linux 7)

In this document I list out the key things to keep in mind when using ASMLib with Multipathed devices

 1. Ensure to have the right Scan order (ORACLEASM_SCANORDER AND EXCLUDE)
to find out the right configuration for your type of multipathing you can refer

https://www.oracle.com/technetwork/server-storage/linux/multipath-097959.html

How to Configure LUNs for ASM Disks using WWID, DM-Multipathing, and ASMLIB on RHEL 5/OL 5 and RHEL 6/OL 6 and RHEL7 (Doc ID 1365511.1)

Remember you will need to put the right value as per the type of your multipathing - Linux Native, Multipathd, Emc etc

2. Ensure to create file /etc/udev/rules.d/99-oracle-asmdevices.rules
This file is used to set the right permissions on reboot of the node.
For this you can refer - 
https://access.redhat.com/solutions/272153
or 
Redhat Reference Document: https://access.redhat.com/sites/default/files/attachments/deploying_oracle_rac_12c_rhel7_v1.2_updated_08-01-2016.pdf 

3. Ensure to start oracleasm.service after multipathd and iscsci
$ cat /usr/lib/systemd/system/oracleasm.service
[Unit]
Description=Load oracleasm Modules
Requires=multipathd.service iscsi.service

After=multipathd.service iscsi.service

The configuration can be quite complex when using multipath devices. In case you are facing any issues you can contact me, I will be glad to help.