VERITAS Volume Manager 4.1 Hardware Notes

Hardware Notes

Disk Array Conﬁgurations Supported for Use with DMP

Chapter 1 11

JBOD Disk Array Support in DMP

NOTE The Dynamic Multipathing feature works with JBOD drives only if the

individual disks provide unique serial number information. If the individual

disks do not provide unique serial numbers, even if the disks are conﬁgured for

multipathing in hardware, Base-VXVM does not provide multipathing support.

DMP supports multipathing of JBOD disk arrays that are connected to a system running

Base-VXVM. These JBOD disk arrays can contain disks from any vendor. However, DMP can

correctly detect multiple paths to the disks in these disk arrays only if the following

conditions are satisﬁed:

• The serial number ﬁeld of the Standard SCSI INQUIRY DATA (bytes 36—47) should be

world wide unique for any disk that is connected to a JBOD. This fact must be known to

the user before the user attempts to conﬁgure DMP to add these disks to the JBOD

category of DMP.

CAUTION If any disk does note provide a unique serial number, DMP cannot detect

multiple paths to the disk correctly and results are unpredictable. Contact

the JBOD disk or disk array vendor to obtain correct information about

unique serial numbers on disks.

• The JBOD disk arrays that require multipathing functionality from DMP should be of the

Active/Active type. This means that all paths to all LUNs on the JBOD disk array should

be simultaneously accessible through all paths, without causing any performance

degradation.

EMC Symmetrix Disk Arrays

The Dynamic Multipathing feature (DMP) of the Volume Manager works with the EMC

Symmetrix disk array only if the disk array is conﬁgured in the Common Serial Number

Mode. This is because only the Common Serial Number Mode conﬁguration provides unique

device identiﬁcation on different paths for DMP to conﬁgure its database. Without this mode,

DMP cannot provide the multipathing functionality. DMP cannot access EMC Symmetrix

disks as individual disks with a single path, it found by scanning the device information tree

in the kernel.

Ultra SCSI and fast-wide differential (FWD) SCSI support has been tested on the EMC OSD

(Open System Director) controller.