ASMLIB Interacting with persistent names generated by udev or devlabel

(Doc ID 372783.1)

Last updated on NOVEMBER 25, 2011

Applies to:

Oracle Server - Enterprise Edition - Version: to - Release: 10.1 to 11.2
Linux x86


For SCSI disks or SAN/NAS devices, Linux discover the disks and assign the names using the the prefix sd*, based on the discovery order.  If a disk configuration occurs, either adding or dropping disks, on the next discovery the name of the disks can change.  This affects single-instance and RAC environments. 

For example, the device originally assigned to the OCR or Voting disk are bound to raw3 and raw4, which are bound to /dev/sdd1 and /dev/sde1   After  storage configuration, raw3 and raw4 are bound to /dev/sde1 and /dev/sdf1.  When CRS is started, it will fail because the content of the disk is not the CRS.   Same situation can happen with ASM disks, causing errors that avoid mounting the diskgroup. 

There are tools like udev or devlabel that generate persistent names under /dev directory.  This names will not change after reboots or storage configuration.  Both work very similar, using unique characteristics to identify the disk and create the name.

In this document we discuss why this tools are not required when implementing ASMLIB.   In addition we give few details about how ASMLIB discovers the disks and how it affects some multipathing technologies.


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