EMC C-bit setting on the array needs to be enabled for VERITAS Volume Manager (tm) for Windows and VERITAS Storage Foundation (tm) for Windows Dynamic Multi-Pathing support

Article:TECH16303  |  Created: 2001-01-24  |  Updated: 2011-01-04  |  Article URL http://www.symantec.com/docs/TECH16303
Article Type
Technical Solution

Product(s)

Environment

Issue



EMC C-bit setting on the array needs to be enabled for VERITAS Volume Manager (tm) for Windows and VERITAS Storage Foundation (tm) for Windows Dynamic Multi-Pathing support


Solution



For the Dynamic Multi-Pathing feature to work correctly with EMC arrays, the EMC C-Bit setting needs to be enabled for the array.

The C Bit
To manage the Multi-Pathing correctly, some hosts need to see identical devices, i.e. identical device serial numbers from each path. EMC arrays have something called the C bit which is a setting on the host interface director on the array. When enabled, the C bit zeroes out the last three bits of the device serial number, thereby presenting the same device serial number and hence, the same devices from both paths. In the above example, the host would be presented with 87010000 from either path.

EMC arrays present devices to the host via a device serial number, AABBBCCD, where:

 
AA is the last two digits of the array that the hypervolume is on
 
BBB is the hypervolume address in Hex
 
CC is the host interface card number
 
D is the port on the card
 

 
If you have two paths from the host to the array and can see device 010 down both paths, you might see the devices presented as 87010010 and 87010160. The last three bits would be different due to their being connected to different host interfaces on the front end of the array.


 


Legacy ID



240462


Article URL http://www.symantec.com/docs/TECH16303


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