HP StorageWorks SAN Virtualization Services Platform Best Practices Guide (5697-0935, May 2011)

7 Hardware
To determine the configuration limits of the current SVSP build, select Tools > Maintenance > Manage
Limits in the VSM GUI and review the displayed information. Knowing the support limitations is
important to ensure you do not exceed the limits, which can result in difficulty troubleshooting
system problems.
Data Path Modules
The Data Path Modules (DPMs) are a key component to the SVSP system. They function by
downloading the mapping tables from the VSM and on-the-fly routing commands from the servers
to the correct location on the back-end LUs. Configuring and load balancing the DPMs properly
will provide maximum value.
Consider the following guidelines:
• DPM ports can only be connected to Fibre Channel switches. Directly connecting to storage,
HBAs, or Fibre Channel hubs is not supported. DPM ports only support fabric mode.
• Hosts and storage can be zoned to different DPM quads to distribute load between the available
DPM ports. For simplicity, HP recommends zoning the same hosts/storage to the same quad
on each DPM, which is called symmetrical configuration. For example, zone hosts A and B
to quad 1 of both DPMs, and zone hosts C and D to quad 2 of both DPMs.
• Zoning hosts and storage to more than one DPM quad is allowed if other scalability limits
(front-end paths, back-end paths, and maximum presentation) are not exceeded. For example,
zone 2 EVAs to quad1, 2 EVAs to quad2 and 2 LSI arrays to quad3; or zone 2 EVAs to quads
1 and 2 and another 2 EVAs to quads 3 and 4.
• All storage must be zoned to all DPM groups.
• Balance workload on the DPMs using the primary/secondary properties of the virtual disk.
Minimize the use of the soft path for I/O to the DPM by:
• Not allowing I/O to cross a 1 MB boundary (the soft path must break up I/O into smaller
chunks). This may be set up in the Fibre Channel HBA.
• Aligning transfers to megabyte boundaries (prior to Windows 2008, Windows did not align
transfers). Use Windows DiskPart on previous Windows versions.
NOTE: Proper SVSP zoning ensures that hosts are prevented from accessing the same virtual
disks on the arrays that are accessed by SVSP (causing data corruption), and to protect hosts from
accessing virtual disks through the VSM that are needed by the VSM for data moving tasks.
Working with DPM groups
When working with multiple DPM groups you may want to partition workloads/assignments among
the groups. For example, suppose you have two DPM groups with two quad cards in each DPM.
You may wish to zone one host of each OS type to each quad in each DPM group. For example:
• Zone all Windows hosts to quad 1 of the DPM group 1.
• Zone all HP-UX hosts to quad 2 of DPM group 1.
• Zone all Solaris hosts to quad 1 of DPM group 2.
• Zone all VMware hosts to quad 2 of DPM group 2.
32 Hardware