5/8/2006 Nicole SAN Protocols 1 Storage Networking Protocols Nicole Opferman CS 526

5/8/2006 Nicole SAN Protocols 2 Objectives  Increase knowledge of storage networking industry  Analyze the emerging storage networking protocols  Learn about the SCSI and Fibre Channel protocols  Determine how TOE fits in

5/8/2006 Nicole SAN Protocols 3 Storage Area Networks (SANs)  High-speed network that connects servers to storage devices  Any-to-any connection doesn’t require a dedicated connection between a server and storage component  No limit to the amount of data that a server can access  Many servers can share a storage unit made up of different storage devices  Can be local or extended over large geographical distances

5/8/2006 Nicole SAN Protocols 4 SCSI Protocol  Small Computer System Interface  Standard interface and command set  Promotes device independence, so it can be used on any hardware  Used by OS for I/O communication with storage devices  Commands are sent as blocks of data from an ‘initiator’ to a ‘target’ in parallel across copper cables

5/8/2006 Nicole SAN Protocols 5 Fibre Channel Protocol  Performs most of its processing in the hardware  High performance, reliable connectivity  Efficient transfer of block data with minimal server intervention  Storage interface to the OS allows HBAs to supply I/O processing  Signals sent through twisted-pair copper wires or fiber optic cables  Topologies: point-to-point, arbitrated loop, switched fabric

5/8/2006 Nicole SAN Protocols 6 iSCSI (Internet SCSI)  Uses TCP/IP to transfer its data  Carries SCSI commands over IP networks  TCP/IP overhead during data transfers  Much cheaper to implement than FC because it only requires an Ethernet interface  IP-based SANs use the same networking technologies for both data and storage networks  TCP/IP can run over nearly any type of physical network  IP networks allow for location-independent data retrieval and storage, which Fibre Channel can’t do

5/8/2006 Nicole SAN Protocols 7 IP Network with iSCSI Devices Source:

5/8/2006 Nicole SAN Protocols 8 How iSCSI Works 1. An end user or an application submits a request 2. The OS generates the corresponding SCSI commands and data requests, which get encapsulated, and possibly encrypted 3. A packet header is added to the resulting IP packets being sent across an Ethernet connection 4. When a packet is received, it is decrypted (if needed) and separated into two parts: the SCSI command and the request 5. The SCSI commands get sent on to the SCSI controller and then to the storage device 6. Since iSCSI is bi-directional, the protocol is also used to return data in response to the original request

5/8/2006 Nicole SAN Protocols 9 TCP/IP Offload Engines (TOEs)  The overhead of TCP/IP processing is the major deterrent to iSCSI storage networks  High TCP overhead in an iSCSI SAN comes from establishing and terminating connections and acknowledging that packets were received  PCI inefficiently transfers small bursts of data from the host across the bus to the network interface integrated circuits  The TOE is a modern technology that is gaining popularity in high-speed Ethernet systems because it optimizes throughput by moving TCP/IP processing to a dedicated sub-system separate from the main host CPU  TOE components are built into a circuit board, either the HBA or the NIC

5/8/2006 Nicole SAN Protocols 10 How TOEs work Source:

5/8/2006 Nicole SAN Protocols 11 Fibre Channel over IP (FCIP)  “Fibre Channel tunneling” or “storage tunneling”  FCIP tunnels FC data between SAN components over IP networks  An IP infrastructure allows geographically distant SANs to be connected for a relatively low cost  Much higher performance than iSCSI  FCIP encapsulates Fibre Channel block data and then transports it over a TCP socket  TCP/IP functions are necessary to set up connectivity between remote SANs

5/8/2006 Nicole SAN Protocols 12 Fibre Channel SAN Source:

5/8/2006 Nicole SAN Protocols 13 iFCP (Internet FC Protocol)  A derivation of FCIP, but iFCP is a routed (gateway-to-gateway) FC protocol  Provides a way to pass data to and from Fibre Channel storage devices in a SAN, or by using TCP/IP in an Internet environment  Can integrate existing Fibre Channel and SCSI networks into the Internet  Has the ability to connect many FC devices to an IP network, combine FC SANs with IP networks, and allows end users to replace a SAN with a TCP/IP network  In an iFCP setting, gateway devices are the midpoint between the FC initiators and target devices

5/8/2006 Nicole SAN Protocols 14 To wrap it up…  FCIP, iSCSI, and iFCP are working towards universal data storage access  Fibre Channel is the best choice for established, highly available storage networks  iSCSI has the potential to provide wide area backup applications and remote access to storage networks  TOEs make iSCSI a much more desirable choice  FCIP can bridge SANs across the WAN  iFCP is ideal for converting a Fibre Channel SAN to an IP SAN, or to update the configuration to allow a combination of both types of networks