Make Linux Disk IDs Visible for UDEV (in VMware)

VMware is a factor

Times and syntaxes change, so it’s time to refresh an old blog post a bit. Especially VMware has established its place in the Oracle world, and it can be tricky to map disk IDs directly into the VM. Many sources recommend to use the SCSI addresses, but I learned to never trust people who have to map devices and do not know for what they will be used.

A prime example is Oracle Real Application Cluster (RAC) – maybe you want a simplified setup on VMware vSpehere in your lab. If you map the same (shared) disk with different SCSI IDs into two different machines, you won’t have too much fun if you think same SCSI ID means same disk. Sounds obvious?

Years ago, I wrote this post about using UDEV to detect Linux devices instead of using ASMlib. Or nowadays, the ASM Filter Driver, because both are surplus additional Oracle software pieces, delivering zero benefit.

Oracle Grid Infrastructure: UDEV fixing ORA-15081: failed to submit an I/O operation to a disk

Prepare VMware

It’s very simple:

1. Set the Extended Parameter for the VM
   “disk.enableUUID=true”
   to get disk serial numbers exposed to the VM at all.
2. If using shared disks (RAC), set SCSI Controller
   “SCSI Bus Sharing”= “Virtual”

You have to stop the VM to be able to change these settings.

Prepare any Linux

First: New Syntax. This applies for all Linux systems.
udevinfo is dead, today scan for device IDs with:

• udevadm info –query=all –path=/sys/block/dm-1
• lsblk -P -o NAME,MODEL,SERIAL,SIZE

Two examples for the /etc/udev/rules.d/99-storage.rules file:

• Multipath
  KERNEL==”dm-“, ENV{DM_MPATH}==”360060e8016023d000001023d00000102″, SYMLINK+=”disk/by-id/ASMREDO1-1″, OWNER:=”oracle”, GROUP:=”oinstall”
• SCSI
  KERNEL==”sd?”, ENV{ID_SERIAL}==”36000c29682376749c24d24fdf4ada978″, SYMLINK+=”disk/by-id/ASMOCW-1″, OWNER:=”oracle”, GROUP:=”oinstall”

Run detection and use the rules:
udevadm trigger

I hope this helps, stay safe and consistent
Martin