VxVM tunable use_hw_replicatedev released to import hardware replicated devices

Description

This article documents the enhanced Veritas Volume Manager (VxVM) functionality to support Hardware Replicated type devices.

New vxdg options were created to ensure all Hardware Replicated type devices are correctly selected during the VxVM import process.

The original design was vxdg -c [-s] -o usereplicatedev=on import <dg-name>

This has since been replaced with the revised -o usereplicatedev=only vxdg option, which must be specifed to import Hardware Replicated type devices, such as EMC SRDF [Metro], Hitachi TrueCopy and many other vendor solutions.

To reduce the effort required to manage and detect Hardware Replicated type devices, Veritas has now introduced the new tunable 'use_hw_replicatedev' with VRTSvxvm public patch 7.4.2.5200 for RHEL7 and RHEL8.

When the tunable use_hw_replicatedev is turned on, the import selection process will detect the presence of Hardware Replicated type devices and automatically call vxdg options -c -o usereplicatedev=only. The enhanced functionality will work for Private and Shared disk groups.

# vxtune | grep rep
use_hw_replicatedev                                      on                          on    N        N

If the tunable use_hw_replicatedev is turned off, the Hardware Replicated type devices will not be imported with the required -c -o usereplicatedev=only import options.

The tunable is enabled by default, but can be turned on or off using the following syntax:

# vxtune use_hw_replicatedev [on|off]

Example

In this instance, the Hardware Replicated disk group srdf_dg1 will be imported automatically with the vxdg recommended import options -c -o usereplicatedev=only as the tunable is turned on.

# rpm -qa VRTSvxvm
VRTSvxvm-7.4.2.5200-RHEL8.x86_64

# vxdg import srdf_dg1
 

# vxdisk -e list
DEVICE       TYPE           DISK        GROUP        STATUS               OS_NATIVE_NAME   ATTR
20-v13_vmdk0_0 auto:LVM       -            -           LVM                  sda              -
emc0_22ba    auto:cdsdisk   emc0_22ba    srdf_dg1    online thinrclm      sde              srdf-r1 tprclm
emc0_22bb    auto:cdsdisk   emc0_22bb    srdf_dg1    online thinrclm      sdf              srdf-r1 tprclm
emc0_22bc    auto:cdsdisk   emc0_22bc    srdf_dg1    online thinrclm      sdg              srdf-r1 tprclm
emc0_22bd    auto:cdsdisk   emc0_22bd    srdf_dg1    online thinrclm      sdh              srdf-r1 tprclm

The same functionality is available for shared disk groups, when the -s option is used with the vxdg command or the Veritas Cluster Server (VCS) CVMVolDg resource.
 

Note: It is vital that the clone_disk not be set when importing Hardware Replicated type devices, hence the vxdg -c option must be used.


The enhanced functionality is currently available on RedHat with InfoScale 7.4.2 and public patch VRTSvxm.7.4.2.4500 and above.

Veritas have started porting the functionality to 8.0.x and it will be released in future public patch releases.

This enhanced functionality is currently being considered by Veritas Technologies LLC to be addressed in future VRTSvxvm public patch releases and other platforms.. Please note that Veritas Technologies LLC reserves the right to remove any fix from the targeted release if it does not pass quality assurance tests or introduces new risks to overall code stability.  Veritas’ plans are subject to change and any action taken by you based on the above information or your reliance upon the above information is made at your own risk.