IP –Based SAN extensions and Performance Thao Pham CS 622 Fall 07

Project Overview  To understand main technologies developed to address long distant replication and backup needs, iSCSI, iFCP and FCIP.  Ways to optimize performance and maximize business return on investment (ROI) when deploying these technologies.

SCSI Transport Protocols

iSCSI iSCSI facilitates block-level initiator-target communication over TCP/IP networks. Thus, iSCSI completes the storage over IP model, which supported only file-level protocols (such as Network File System [NFS], Common Internet File System [CIFS], and File Transfer Protocol [FTP]). iSCSI facilitates block-level initiator-target communication over TCP/IP networks. Thus, iSCSI completes the storage over IP model, which supported only file-level protocols (such as Network File System [NFS], Common Internet File System [CIFS], and File Transfer Protocol [FTP]).

iSCSI

PDUs

iSCSI Sessions and Connections  Sessions are classified in normal or discovery. iSCSI commands are in normal sessions.  discovery session is used exclusively for iSCSI target discovery

iSCSI deployment

iFCP  iFCP is a gateway-to-gateway protocol, which provides Fibre Channel fabric services to Fibre Channel devices over a TCP/IP network. iFCP uses TCP to provide congestion control, error detection and recovery. iFCP's primary objective is to allow interconnection and networking of existing Fibre Channel devices at wire speeds over an IP network.

iFCP deployment

iFCP Connection Flow  Following data-link layer initialization, IP initialization occurs.  iFCP gateways discover each other via iSNS.  Configuration parameters for the iFCP fabric are discovered via iSNS.  IPsec connection is optionally established between each pair of iFCP gateways once the iFCP fabric parameters are known  The iSNS then propagates the information to each of the other iFCP gateways.  each iFCP gateway updates the FCNS of its attached FC-SAN with the remote node information and creates an entry in its address translation table for the remote node.  iFCP fabric is ready for initiator-target communication.  TCP connection proactively or on request of PLOGI

FCIP  Fibre Channel Over TCP/IP (FCIP) describes mechanisms that allow the interconnection of islands of Fibre Channel storage area networks over IP-based networks to form a unified storage area network in a single Fibre Channel fabric.

FCIP deployment concept

FCIP tunneling Flow  IP initialization occurs.  The FCIP tunnel parameters configured or discovered (via SLPv2) IPsec connection (optional) follows.  TCP connection establishment.  The tunnel initiator transmits an FC Special Frame (FSF). FC identifier, identifier of the tunnel initiator, target, and a 64-bit randomly selected number that uniquely identifies the FSF.  The receiver verifies FSF match its local configuration. FSF is echoed back to the tunnel initiator.  After the tunnel initiator receives and verifies the FSF, the FCIP tunnel may carry FC traffic.

HP’s XP and EVA storage FCIP using HP Continuous Access

End devices include hosts or target storage devices, and fabric services include routing, device discovery, management, authentication, and inter-switch communication.

Performance based on distance

Performance function on packet loss (at 1500km)

iFCP and iSCSI Performance based on bandwidth iFCP iSCSI

Performance Parameters Tuning  Increasing TCP window size (depending on round trip delay (distance) and bandwidth.  Use of Jumbo Frames (bigger than 1514 bytes up to 9000 bytes) -> reduce frame rate.  Increasing FC buffer credit -> increasing number of frames to be sent before stopping to wait.  Zero copy: data is written to application directly, bypassing memory copy as in TCP (iSCSI does not yet support this).  Parallel TCP sessions: enables more efficient use of available bandwidth, not supported in FCIP.  Choosing asynchronous vs. synchronous replication.  Distance consideration -> reduce latency.

Increase in Window size iSCSI iFCP

Parallel TCP sessions iFCP iSCSI

Conclusion  Depending on cost and size of companies, iSCSI are relatively cheaper for companies without a SAN. Performance can be improved by network parameters and TOE technologies.  iFCP and FCIP have high performance throughput, but they are more costly, require hardware implementation and SAN infrastructure already in place.

References:  Storage Area Network Extension Solutions and Performance Assessement by Radha Telikepalli, Tadeusz Drwiega, and James Yang  Overview of Modern SCSI Networking Protocols, by James Long  IETF  HP Continuous Access XP and EVA  HP SR2122-2