User guide

Technical white paper | HP Enterprise Virtual Array Storage and VMware vSphere 4.x and 5.x configuration best practices
23
All the same facts listed above for the 1GbE iSCSI Module apply to the 10GbE iSCSI Module. As in Table 2 above, the
highlighted cell in Table 3 is the intersection of configuration options that provides the best balance of high availability and
GbE port bandwidth for the 10GbE iSCSI Module configuration.
Best practices for 10GbE iSCSI Module configuration
• When all 10GbE ports are connected to the iSCSI SAN and two NICs are used at the host, use Dynamic discovery to simply
configuration and meet adequate high availability with a 10GbE iSCSI Module option.
Performance consideration
When connecting ESX via iSCSI to an HP EVA, note that there is no performance gain from using different iSCSI LUN groups.
As previously discussed the groups primarily provide additional LUN count access. For simplicity, it may be worthwhile
separating iSCSI LUNs into different groups based on application or departmental usage for easier tracking of resources.
Because of the ESX limitation of eight paths per LUN for iSCSI, administrators need to carefully tradeoff their need for
performance over availability. In a 1GbE iSCSI Module configuration, utilizing as many 1GbE Ethernet ports at the array side
as possible will likely provide the highest performance boost but reduce the high availability of the system. In a 10GbE iSCSI
Module configuration, an administrator can achieve higher availability by adding additional host connections to the iSCSI SAN
with a smaller number of 10GbE ports while maintaining adequate performance.
Best practices for iSCSI performance and availability
• Using two iSCSI GbE ports at the array and two NICs on the ESX host provides the most flexible option to achieve the right
balance of ease of configuration, high availability and performance for the 10GbE iSCSI Module configuration options.
• For the 1GbE iSCSI Module configuration option, using static discovery to limit the number of iSCSI targets used per GbE
port to 1 can help achieve increased high availability and performance at the cost of ease of configuration.
Note
The HP EVA MPX200 configuration will work exactly as described above for 1GbE iSCSI Module and 10GbE iSCSI Module
options. However, the MPX200 is capable of exporting LUNs for up to four different arrays at the same time.
The HP EVA does not currently support exporting a LUN to a host via iSCSI while simultaneously exporting this same LUN via
Fibre Channel.
Implementing multi-pathing in vSphere 4.x and 5.x
A key task when configuring vSphere 4.x and 5.x is to set up multi-pathing so as to optimize the connectivity and operation
of the EVA array. In addition, advanced tuning of HBAs, virtual SCSI adapters and ESX advanced parameters can help you
increase storage performance.
vSphere 4 introduced the concept of path selection plug-ins (PSPs), which are essentially I/O multi-pathing options. These
plug-ins are described in more detail in Configuring multi-pathing.
Table 4 outlines multi-pathing options in vSphere 4.x and 5.
Table 4. Multi-pathing options
I/O path policy
PSP
vSphere 4
vSphere 4.1
vSphere 5
MRU
VMW_PSP_MRU
Yes
Yes
Yes
Round Robin
VMW_PSP_RR
Yes
Yes
Yes
Fixed
VMW_PSP_FIXED
Yes
Yes
Yes
(Fixed = Fixed_AP)
6
Fixed_AP (Array Preference)
VMW_PSP_FIXED_AP
No
Yes
6
On vSphere 5.x, the FIXED I/O path policy when attached to an ALUA capable array operates like the FIXED_AP policy in vSphere 4.1.