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Network Design Guidelines of Configuring
EqualLogic iSCSI
This article provides guidelines for designing networks for using EqualLogic
iSCSI with a cluster.
Typically you will have a minimum of three networks in use:
• Public networks for applications. A data network can be made redundant
using NIC teaming or by using multiple interfaces on separate subnets.
• Private network also called as Heartbeat network. NIC teaming cannot be
used
on the Private network.
• Storage area network (SAN). The SAN can be made
redundant by use of Microsoft’s
multipath I/O (MPIO). NIC teaming can be used in a SAN; however, multipath
I/O provides
more intelligent, SAN-integrated load balancing capabilities.
Each network (public or private) connecting the nodes of a cluster must be
configured as a
unique IP subnet. The IP subnet numbers for the networks connecting the
cluster nodes must be
different. For example, if a cluster node has multiple adapters attached to
the same cluster
network (and NIC teaming is not in use), only one adapter will be used by
the Cluster service; the
others will be ignored. A node having two or more network adapters without
NIC teaming
connected to the same network will not provide fault tolerance or load
balancing and is not
recommended.
It is recommended that each public network and SAN be configured in a
redundant fashion to
provide the benefit of a no-single-point-of-failure configuration. This
configuration would
include multiple network switches so that each network can operate (and
fail) independently.
The SAN must be a network separate from each public network and private
network. On the SAN, each cluster node must have network connectivity to the
iSCSI group IP address. You can configure the SAN on the same or separate
switches as the public and private networks. If using the same switches, you
must use separate VLANs and TCP/IP subnets for each network. On your SAN,
you can use either the Microsoft iSCSI Software Initiator or iSCSI HBAs.
When using iSCSI HBAs, ensure that you configure these cards to use Storport
drivers.
For optimal performance and high availability, EqualLogic recommends
following these SAN
network guidelines:
• Use a switched, Gigabit Ethernet network. The connection is 10 and 100
Mbits, the performance will be significantly degraded.
• Utilize fast convergence/fast spanning tree. You will need to consult your
switch manufacturer’s documentation to verify if your switches are
RSTP-capable and how to configure for RSTP.
• Use flow control. Enable Flow Control on each switch port that handles
iSCSI traffic. If
your server is using a software iSCSI initiator and NIC combination to
handle iSCSI traffic,
you must also enable Flow Control on the NICs to obtain any performance
benefit.
• Enable Jumbo Frames. If supported by all the devices in the network path
between hosts and
arrays, enable Jumbo Frames on each switch that handles iSCSI traffic. This
support is
usually disabled by default. If your server is using a software iSCSI
initiator and NIC
combination, you must also enable Jumbo Frames on the NICs that handle iSCSI
traffic to
obtain any performance benefit and ensure consistent behavior.
• Configure multiple network interfaces on an array. Connect them to
different switches.
• For a multi-subnet iSCSI group, provide access to the subnet on which the
group IP
address for all enabled network interfaces on the group members.
• Use redundant paths between iSCSI initiators and storage arrays. Multipath
I/O ensures that
no single point of failure exists between initiators and arrays. This can be
achieved by using
Microsoft’s MPIO solution.
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