Configure Vxvm Load Balancing In A/p Dmp

Document ID: 266269 http://support.veritas.com/docs/266269 How to configure load balancing across multiple primary paths in an Active/Passive DMP environment using VERITAS Volume Manager (tm) 4.0 Details: In an Active/Passive Dynamic Multipathing (DMP) environment, it is possible that there may be multiple primary paths to a device due to a mesh of SAN switches. Volume Manager 4.0 can be configured to allow load balancing across multiple primary paths. This TechNote explains how to do this. Note: This feature was not available in releases prior to 4.0 In the following example, device c3t2d15 belongs to a disk group named tonydg and contains a simple concatenated volume named tony1. The device has eight primary paths: # vxdisk list c3t2d15s2 Device: c3t2d15s2 <..snip..> numpaths: 8 c2t0d15s2 state=enabled c2t1d15s2 state=enabled c3t1d15s2 state=enabled c3t2d15s2 state=enabled c4t3d15s2 state=enabled c4t4d15s2 state=enabled c5t3d15s2 state=enabled c5t5d15s2 state=enabled

type=primary type=primary type=primary type=primary type=primary type=primary type=primary type=primary

DMP statistics are enabled and a read based workload is applied to the volume: #vxdmpadm iostat start #dd if=/dev/vx/rdsk/tonydg/tony1 of=/dev/null bs=512k count=6144 By displaying the DMP statistics for device c3t2d15, it can be seen that all I/Os are being directed to one subpath, c5t5d15: # vxdmpadm iostat show dmpnodename=c3t2d15s2 cpu usage = 8023us per cpu memory = 32768b OPERATIONS MBYTES AVG TIME(ms) PATHNAME READS WRITES READS WRITES READS WRITES c2t0d15s2 0 0 0 0 0.000000 0.000000 c2t1d15s2 0 0 0 0 0.000000 0.000000 c3t1d15s2 0 0 0 0 0.000000 0.000000 c3t2d15s2 0 0 0 0 0.000000 0.000000 c4t3d15s2 0 0 0 0 0.000000 0.000000 c4t4d15s2 0 0 0 0 0.000000 0.000000 c5t3d15s2 0 0 0 0 0.000000 0.000000 c5t5d15s2 6144 0 3145728 0 0.011081 0.000000 Using vxdmpadm, it is clear that the default iopolicy for this enclosure is Single Active (which explains the above behavior): # vxdmpadm getattr enclosure HDS92000 iopolicy ENCLR_NAME DEFAULT CURRENT

============================================ HDS92000 Single-Active Single-Active To load balance across multiple primaries, the iopolicy should be set to roundrobin: # vxdmpadm setattr enclosure HDS92000 iopolicy=round-robin # vxdmpadm getattr enclosure HDS92000 iopolicy ENCLR_NAME DEFAULT CURRENT ============================================ HDS92000 Single-Active Round-Robin The DMP statistics are reset and the same workload is applied to the volume, load balancing across the primary paths can be seen. #vxdmpadm iostat reset #dd if=/dev/vx/rdsk/tonydg/tony1 of=/dev/null bs=512k count=6144 #vxdmpadm iostat show dmpnodename=c3t2d15s2 cpu usage = 7223us per cpu memory = 32768b OPERATIONS MBYTES AVG TIME(ms) PATHNAME READS WRITES READS WRITES READS WRITES c2t0d15s2 786 0 402432 0 0.011013 0.000000 c2t1d15s2 778 0 398336 0 0.011267 0.000000 c3t1d15s2 772 0 395264 0 0.011205 0.000000 c3t2d15s2 744 0 380928 0 0.011094 0.000000 c4t3d15s2 750 0 384000 0 0.011029 0.000000 c4t4d15s2 768 0 393216 0 0.011169 0.000000 c5t3d15s2 733 0 375296 0 0.010943 0.000000 c5t5d15s2 813 0 416256 0 0.011068 0.000000 The enclosure can be returned to its default policy of single active with the following: # vxdmpadm setattr enclosure HDS92000 iopolicy=singleactive Note: This setting is not persistent across reboots, I/O policies will revert to their default. Persistence can be configured by adding the relevant vxdmpadm command to a boot script. Acknowledgements DMP development team Products Applied: Volume Manager for UNIX/Linux 4.0 (Solaris) Last Updated: March 12 2004 07:37 PM GMT Expires on: 365 days from publish date Subscribe Via E-Mail IconSubscribe to receive critical updates about this document Subjects: Volume Manager for UNIX/Linux Application: Configuration, How To Languages: English (US) Operating Systems: Solaris

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