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
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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
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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
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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
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Nicole SAN Protocols

7. IP Network with iSCSI Devices
Source:
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8. How iSCSI Works An end user or an application submits a request
The OS generates the corresponding SCSI commands and data requests, which get encapsulated, and possibly encrypted
A packet header is added to the resulting IP packets being sent across an Ethernet connection
When a packet is received, it is decrypted (if needed) and separated into two parts: the SCSI command and the request
The SCSI commands get sent on to the SCSI controller and then to the storage device
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
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Nicole SAN Protocols

10. How TOEs work 5/8/2006 Nicole SAN Protocols
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 5/8/2006 Nicole SAN Protocols
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
5/8/2006
Nicole SAN Protocols