Download IP –Based SAN extensions Performance

IP –Based SAN extensions
and Performance
Thao Pham
CS 622
Fall 07
Project Overview
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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
PDUs
iSCSI Sessions and Connections
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Sessions are classified in normal or discovery. iSCSI
commands are in normal sessions.
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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
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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
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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
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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 http://tools.ietf.org/html/rfc3821
 HP Continuous Access XP and EVA
 HP SR2122-2