An iSCSI switch is an appliance that processes and channels data between an iSCSI initiator and target on a storage device. ISCSI traffic is typically high speed, high volume and needs to be delivered with minimal latency. An iSCSI switch must be able to process continuous data at 1 Gbps on all ports at the same time.
Unlike specialized Fibre Channel SAN switches, iSCSI switches are standard Ethernet networking switches that can be used for iSCSI traffic optimization. iSCSI switches are not even required. When using iSCSI storage, an iSCSI initiator can perform some of the same basic functions a switch could be used for. An iSCSI initiator is typically free, and connects external iSCSI-based storage to host computers with an Ethernet network adapter.
However, utilizing a switch specifically for storage has benefits. iSCSI switches offer reliability, strengthen network control and support Quality of Service.
Other switch features that can benefit iSCSI include:
- Flow control: Using flow control can help a host avoid becoming overwhelmed with the high traffic associated with iSCSI storage by giving the host control over the rate at which it receives data. Flow control can also help prevent packet loss, avoiding added latency in iSCSI storage networks.
- Jumbo frames: The high payload of jumbo frames can make data transmissions more efficient by giving the switch fewer frames to process. This can improve iSCSI performance, but there is a higher cost associated with using jumbo frames that might not outweigh the benefits for some organizations.
- Link aggregation: Also known as "port trunking," this feature combines switch ports into higher bandwidth trunks in order to increase throughput and create redundancy.
iSCSI switches are a relatively cheap addition to iSCSI storage. Switch options can range from basic, with no additional features, to advanced. Switches used for iSCSI SANs can cost around $400 to $600 per port.