vSphere Storage - ESXi 5.1 - Documentation - VMware
vSphere Storage - ESXi 5.1 - Documentation - VMware
vSphere Storage - ESXi 5.1 - Documentation - VMware
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Generally, applications or systems that write a lot of data to storage, such as data acquisition or transaction<br />
logging systems, should not share Ethernet links to a storage device. These types of applications perform best<br />
with multiple connections to storage devices.<br />
Multiple Connections from Switch to <strong>Storage</strong> shows multiple connections from the switch to the storage.<br />
Figure 14-3. Multiple Connections from Switch to <strong>Storage</strong><br />
1 Gbit<br />
1 Gbit<br />
1 Gbit<br />
1 Gbit<br />
Using VLANs or VPNs does not provide a suitable solution to the problem of link oversubscription in shared<br />
configurations. VLANs and other virtual partitioning of a network provide a way of logically designing a<br />
network, but do not change the physical capabilities of links and trunks between switches. When storage traffic<br />
and other network traffic end up sharing physical connections, as they would with a VPN, the possibility for<br />
oversubscription and lost packets exists. The same is true of VLANs that share interswitch trunks. Performance<br />
design for a SANs must take into account the physical limitations of the network, not logical allocations.<br />
Checking Ethernet Switch Statistics<br />
Many Ethernet switches provide different methods for monitoring switch health.<br />
Switches that have ports operating near maximum throughput much of the time do not provide optimum<br />
performance. If you have ports in your iSCSI SAN running near the maximum, reduce the load. If the port is<br />
connected to an <strong>ESXi</strong> system or iSCSI storage, you can reduce the load by using manual load balancing.<br />
If the port is connected between multiple switches or routers, consider installing additional links between these<br />
components to handle more load. Ethernet switches also commonly provide information about transmission<br />
errors, queued packets, and dropped Ethernet packets. If the switch regularly reports any of these conditions<br />
on ports being used for iSCSI traffic, performance of the iSCSI SAN will be poor.<br />
iSCSI SAN Configuration Checklist<br />
This topic provides a checklist of special setup requirements for different storage systems and <strong>ESXi</strong> hosts.<br />
Table 14-2. iSCSI SAN Configuration Requirements<br />
Component Comments<br />
All storage systems Write cache must be disabled if not battery backed.<br />
Topology No single failure should cause HBA and SP failover, especially with active-passive storage<br />
arrays.<br />
EMC Symmetrix Enable the SPC2 and SC3 settings. Contact EMC for the latest settings.<br />
EMC Clariion Set the EMC Clariion failover mode to 1 or 4. Contact EMC for details.<br />
HP MSA No specific requirements<br />
HP EVA For EVA3000/5000 firmware 4.001 and later, and EVA4000/6000/8000 firmware 5.031 and<br />
later, set the host type to <strong>VMware</strong>.<br />
Otherwise, set the host mode type to Custom. The value is:<br />
n EVA3000/5000 firmware 3.x: 000000002200282E<br />
n EVA4000/6000/8000: 000000202200083E<br />
Chapter 14 Best Practices for iSCSI <strong>Storage</strong><br />
NetApp If any of your iSCSI initiators are a part of an initiator group (igroup), disable ALUA on the<br />
NetApp array.<br />
<strong>VMware</strong>, Inc. 131
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