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Technical white paper | HP StoreVirtual 4000 Storage

VLAN

A VLAN is a logical grouping of devices that share the same broadcast domain with a common set of network

requirements. For StoreVirtual, the network should be isolated from other networks, either by using VLANs or separate

network equipment.

VLANs allow for a logical segmentation of a single physical switch. A port which is a member of one VLAN cannot

communicate with ports which are on another VLAN; this creates separate networks segments on a single switch. A

single port is typically a member of one “native” VLAN; however, ports can also carry trac from multiple VLANs. This

means that all frames which are not on the native VLAN of this port are tagged with the VLAN ID. This is true for all

incoming and outgoing frames on that port.

HP StoreVirtual 4000 Storage does not natively support tagged VLANs. If HP StoreVirtual 4000 Storage is on a separate

iSCSI VLAN, the appropriate switch ports must be in the iSCSI VLAN (untagged for iSCSI VLAN; primary VLAN ID must be

set to the VLAN ID of the iSCSI VLAN).

Best practices

• Isolate iSCSI trac on its own network segment (separate VLAN or dedicated network infrastructure), thus separating

management and general production trac on separate VLANs.

• The preferred protocol for combining two or more physical VLAN tagged uplinks between switches to aggregate

bandwidth while providing fault tolerance is the link aggregation control protocol (802.3ad).

• Plan for redundant network paths exist between all interconnected switches allowing an alternative path for trac to

traverse in the case of a primary path failure.

Spanning Tree Protocol

Spanning Tree Protocol (STP) is a link management protocol that detects and prevents loops in an Ethernet network

by helping ensure that only one active path exists between two or more interconnected switches. There are several

enhanced versions of the common STP protocol, that have evolved over the years oering faster convergence of the STP

protocol. HP recommends using either Rapid STP (RSTP) or Multiple STP (MSTP) for loop prevention and path fail-over to

support a fault-tolerant IP storage network.

RSTP is simplest of the two protocols to congure. RSTP operates independent of network VLAN conguration, and

employs a single spanning tree instance throughout the Layer 2 bridged network. RSTP protocol blocks physical

redundant links within a switched network. Blocked links are available as failover paths.

MSTP allows for the design of multiple STP instances over 802.1q links (tagged links) MSTP enables VLANs to be mapped

to the spanning-tree instance. MSTP provides multiple forwarding paths for data trac and enables load balancing.

It improves the fault tolerance of the network because a failure in one STP instance, or forwarding path, does not

necessarily aect other STP instances forwarding for the other VLANs. In simple terms, an MSTP instance is the mapping

of a particular set of VLAN to a single instance. MSTP oers advanced STP features and is more complex to congure and

design than RSTP.

HP Storevirtual 4000 White Paper

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