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[T Series]A Drive Letter Generating Mechanism Defect on Mac OS X Led to a Drive-Letter-Shift Issue

Publication Date:  2012-07-19 Views:  413 Downloads:  0

Issue Description

Product and version information:

  • S5500T V100R001 V100R002
  • S5600T V100R001 V100R002
  • S5800T V100R001 V100R002
  • S6800T V100R001 V100R002
  • Application server operating system: Mac OS X series

After the host was restarted or the link between the host and the storage array was disconnected (for example, the optical fiber was removed), the drive letter for the LUNs mapped from the storage array changed. This drive-letter-shift issue led to read/write errors.

1.We mapped four LUNs in the following sequence: LUN1, LUN2, LUN3, LUN4. The corresponding drive letters generated for these LUNs were disk1, disk2, disk3, disk4.
2.We disconnected the link by restarting the host or removing the optical fiber.
3.The drive letters may change: LUN2 to disk 2, and LUN3 to disk 3.

Alarm Information


Handling Process

1.The Mac OS X system automatically mounts volumes to the Volumes directory. The Mac OS X system can directly use the volumes created for the disks; therefore, drive-letter-shift issues are avoided.
2.To avoid drive-letter-shift issues, you can use volume UUIDs by changing the mounting directory of volumes, and therefore avoided the use of disk file names. Procedure:

  • Step 1: Run the diskutil info test command to obtain volume UUIDs.
  • Step 2: Create or modify the /ect/fstab file, and add the volumes that need to be automatically mounted. The command syntax is UUID=[Volume UUID] [mount point] [fstype] [rwtype].

For example, if you want disk0s1 to be automatically mounted to the /var/root/test directory, perform the following steps:

  • Step 1: Run the diskutil info test /dev/disk0s1 command to obtain its UUID.
    Figure 1
  • Step 2: Run the vi /etc/fstab command to create or modify the fstab file, and add the volumes that need to be mounted to this file.
    Figure 2

Root Cause

1.The Mac OS X system generates disk files in the sequence the disks are connected.
2.When the disks are connected again after a disconnection but in a different sequence, the corresponding disk file names change, that is, a drive-letter-shift issue occurs.


1.Check whether any drive-letter-shift issues occur when restarting a host, storage array, or removing and reinserting an optical fiber. Drive-letter-shift issues cause read/write errors.
2.It is recommended that you create volumes and use the volumes to perform drive-letter-related operations.