z-iscsi-internet small computer system interface-seminar report
TRANSCRIPT
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INTRODUCTION
The SCSI protocols widely used to access storage devices. The iSCSI
protocol is a transport for SCSI over TCP/IP. SM-2 defines an architecture
model for SCSI transports, and iSCSI defines such a transport on top of
TCP/IP. Other SCSI transports include SCSI Serial and Fibre Channel Protocol
(FCP). Until recently standard networking hardware (Ethernet) and IP-based
protocols could not provide the necessary high bandwidth and low latency
needed for storage access. With the recent advances in Ethernet technology, it
is now practical from a performance perspective to access storage devices over
an IP network. 1Gb Ethernet is now widely available and is competitive with
current 1 and 2 Gb Fibre Channel technology. 10Gb Ethernet will soon also be
widely available. Similar to FCP, iSCSI allows storage to be accessed over a
storage area network (SAN), allowing shared access to storage. A major
advantage of iSCSI over FCP is that iSCSI can run over standard off-the-shelf
network components, such as Ethernet. Furthermore, iSCSI can exploit IP-
based protocols such as IPSec, for security and Service Location Protocol
(SLP) for discovery. A network that incorporates iSCSI SANs need use only a
single kind of network infrastructure (Ethernet) for both data and storage
traffic, whereas use of FCP requires a separate kind of infrastructure (Fibre
Channel) for storage (Fig.2). IP based SANs using iSCSI can be managed
using existing and familiar IP-based tools such as Simple NetworkManagement Protocol (SNMP) whereas FCI SANs require specialized
management infrastructure. Furthermore, iSCSI-based SANs can extend over
arbitrary distances, just like TCP, and are not subject to distance limitations
that currently limit FCP.
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Fig(1)
Fig.(2) Classic SAN vs iSCSI
In addition to iSCSI, several other protocols have been defined to
transport storage over an IP network. FCIP is used to connect separate islands
of Fibre Channel SANs over an IP network to form a single unified SAN. iFCP
is a gateway-to-gateway protocol for the implementation of Fibre Channel
fabric functionality on a network in which TCP/IP switching and routing
elements replace Fibre Channel components. Whereas, FCIP and iFCP are
used to allow the connection of existing Fibre Channel infrastructures to each
other and to IP network. iSCSI enables the creation of SANs complete
independent of Fibre Channel.
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FACTORS ENABLING IP STORAGE
SAN deployments have been driven by an insatiable demand for storage
and the user benefits delivered by networked storage. These benefits include
efficient storage. These benefits include efficient storage utilization through
storage consolidation, the ability to manage more storage capacity, rapid
deployment of new storage, higher availability, and faster backup and restore
operations.
With the recent development of the iSCSI protocol and silicon-based
TCP/IP offload engines, SANs based TCP/IP networks are now possible. The
IP networking infrastructure includes multi-gigabit networks, sophisticated
bandwidth allocation and network management tools, and the ubiquitous reach
of IP and Ethernet. These factors together enable new IP Storage solutions,
using iSCSI protocol.
Fig.3 Factors enabling iSCSI storage
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LEVERAGING THE BEST FROM STORAGE AND
NETWORKING
iSCSI builds on the two most widely used protocols from the storage and
the networking worlds. From the storage side, the iSCSI used the SCSI
command set, the core storage commands used throughout all storage
configurations.
On the networking side, iSCSI uses IP and Ethernet, which are the basis
for the most corporate networks, and are increasingly being used for
metropolitan and wide area networking as well. With almost eighty years of
research, development and integration, IP networks provide the almost in
manageability, interoperability and cost-effectiveness.
Fig.4 Leveraging SCSI and IP for Storage Fig.5 iSCSI Protocol
Network Stack
Fig.4 shows how SCSI is mapped to TCP/IP through the
discs layer, freeing SCSI from its parallel bus structure.
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Fig.5 shows a simplified version of a protocol stack
including iSCSI. Use of the standard SCSI command set facilities
interoperability with existing operating system and applications that lay above
that layer. Additionally, use of a standard TCP/IP network provides universal
reach to the global IP infrastructure.
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ADVANTAGES OF IP STORAGE
*Familiar network technology and management
Reduces training and staff cost
*Proven transport infrastructure
Increases reliability
*Transition from 1Gigabit Ethernet to 10 Gigabit Ethernet and beyond
Protects investment with simplified performance upgrades
*Scalability over long distances
Enables remote data replication and disaster recovery
*Brings Ethernet economics to storage
Enables lower total cost of ownership
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ELEMENTS OF IP STORAGE NETWORKING
IP Storage Networking refers to computer systems and storage
elements that are connected via IP. It also refers to the IP infrastructure
transporting storage traffic among these targets. Fig.6 shows the various
elements of an IP storage network.
The first element, Device I/O, refers to computer systems and
storage resources that have native IP interfaces. These could include servers,
disk arrays or tape libraries with an iSCSI adapter or iSCSI controller. The
interfaces typically are Ethernet and include protocol processing, such as
TCP/IP offload engines to reduce processing loads on the host devices.
The second element of an iSCSI storage area network is the fabric of
switches. The advantage of an IP based fabric is that users can create a SAN
using standard Ethernet switches and routers to transport data over the SAN
fabric. The fabric also may include storage routers and switches that have a
combination of iSCSI interfaces and other storage interfaces such as SCSI or
Fiber Channel. Storage switches and routers provide multi-protocol
connectivity not available in conventional IP and Ethernet switches. They also
provide storage specific functionality, such as peer-to-peer copy commands.
The third element of IP storage networking is the SAN
interconnection. Since iSCSI is a native IP based protocol, SAN
interconnection does not require storage-specific functionality and can use a
shared or dedicated IP/Ethernet network.
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Fig.6 Segments of Storage Networking
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iSCSI DEFINED
Internet SCSI (iSCSI) is a draft standard protocol for encapsulating SCSI
command into TCP/IP packets and enabling I/O block data transport over IP
networks. iSCSI can be used to build IP-based SANs. The simple, yet powerful
technology can help provide high-speed, low-cost, long-distance storage
solution for Web sites, service providers, enterprises and other organizations.
An iSCSI HBA, or storage NIC, connects storage resources over Ethernet. As
a result, core transport layers can be managed using existing network
management applications. High-level management activities of the iSCSI
protocol such as permissions, device information and configuration can
easily be layered over or built into these applications. For this reason, the
deployment of interoperable, robust enterprise management solutions for
iSCSI devices is expected to occur quickly.
First-generation iSCSI HBA performance is expected to be well suited
for the workgroup or departmental storage requirements of medium- and large-
sized businesses. The expected availability of TCP/IP Offload Engines in 2002
will significantly improve the performance of iSCSI products. Performance
comparable to Fibre Channel is expected when vendors begin shipping 10
Gigabit Ethernet iSCSI products in 2003.
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Fig 7. Layered View
BENEFITS OF ISCSI
By combining SCSI, Ethernet and TCP/IP, Gigabit iSCSI delivers these
key advantages: Builds on stable and familiar standards many IT staffs are familiar with
the technologies
Creates a SAN with a reduced TCOinstallation and maintenance costs arelow since the TCP/IP suite reduces the need for hiring specialized
personnel
Provides a high degree of interoperabilityreduces disparate networks andcabling, and uses regular Ethernet switches instead of special Fibre
Channel switches
Ethernet transmissions can travel over the Global IP Network and thereforehave no practical distance limitations
Scales to 10 Gigabit comparable toOC-192 SONET (SynchronousOptical Network) rates in Metropolitan Area Networks (MANs) and Wide
Area Networks (WANs)
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WHO CAN USE IT
iSCSI SANs are most suitable for organizations with a need for
streaming data and/or large amounts of data to store and transmit over the
network.
This includes:
Internet Service Providers (ISPs)
Storage Service Providers (SSPs) Organizations that need remote data replication and disaster recovery. For
example, a high-technology company in San Jose remains susceptible to
disaster if it uses a Fibre Channel SAN. Original and backup data copies
could be lost in the same earthquake due to distance limitations.
Geographically distributed organizations that require access to the samedata on a real-time basis. For example, work team members who need the
latest project data without waiting 24 hours for traditional
replication/backup/ reconciliation procedures.
Businesses and institutions with limited IT resources, infrastructure andbudget. These organizations should look for iSCSI equipment those
functions over standard Gigabit Ethernet Cat-5 copper cabling already in
place in most buildings today.
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ISCSI FEATURES
TCP
TCP was chosen as the transport for iSCSI. TCP has many features that
are utilized by iSCSI :
1. TCP provides reliable in-order delivery of data.2. TCP provides automatic retransmission of data that was not
acknowledged.
3. TCP is a friendly network citizen in that it provides the necessary flowcontrol and congestion control to avoid overloading a congested
network.
4. TCP works over a wide variety o physical media and interconnecttopologies.
While other protocols such as SCTP also provide many of these
features, TCP has the advantage of having been deployed for decade and is
therefore better understood and more widely available.
SESSIONS
SCSI commands are typically issued by a storage initiator (client) to a
storage target (server). The relationship between SCSI entities is referred as
nexus. The iSCSI entity corresponding to an I_T_NEXUS (initiator-target
nexus) is an iSCSI session. An iSCSI session is a collection of TCP
connections between an iSCSI initiator and an iSCSI target used to pass SCSI
commands are data between the initiator and the target.
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Even though a single TCP connection is sufficient to establish
communication between an initiator and a target, it is often advantageous use
multiple connections:
1. It is often not possible to achieve the maximum bandwidth of theunderlying physical interconnect using only a single TCP connection.
2. When working on a multiprocessor machine, it may be advantageous toallow separate threads running on the different processors to
simultaneously utilize different TCP connections.
3. If there are more than one physical interconnect between the initiatorand the target, spreading multiple TCP connections over all the possible
physical interconnects can aggregate their bandwidth.
ISCSI PROTOCOL DATA UNITS
iSCSI defines its own packets, referred to as iSCSI protocol data
units (PDUs). iSCSI PDUs consist of a header and possible data, where the
data length is specified within the iSCSI PDU header. An iSCSI PDU is sent as
the contents of one or more TCP packets.
The most commonly used iSCSI PDU types are :
(i) SCSI Command/Response.(ii)
Data In/Out
(iii) Ready to Transfer (R2T).(iv) Login Request/Response.
The SCSI Command PDU is used to transfer a SCSI command
from the initiator to the target. If the SCSI commands requests to read data
from the target, the target will send the data to the initiator in one or more Data
In PDUs. If the SCSI command requests to write data to the target, the initiator
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will send data to the target in one or more Data Out PDUs. The target may
specify to the initiator which part of the data to send by sending to the initiator
an R2T PDU. Upon completion of the entire data transfer, the target sends a
SCSI Response PDU to the initiator indication either successful completion of
the command or any error condition detected. For each SCSI Command PDU
there is a corresponding single SCSI Command PDU there is a corresponding
single SCSI Response PDU, but possibly multiple (or no) Data PDUs. SCSI
Data and Response PDUs must be sent over the same TCP connection on
which their corresponding SCSI Command PDU was issued.
LOGIN
Immediately upon establishing a TCP connection between an
iSCSI initiator and iSCSI target, a login procedure must be performed. The
initiator sends a Login Request PDU to the target. The initiator and target may
authenticate each other and may negotiate operational parameters. A default
authentication method, Challenge-Handshake Authentication Protocol
(CHAP), must be supported by all compliant iSCSI implementations. Some of
the operational parameters that may be negotiated are the maximum number of
connections to be used in the session, the amount of unsolicited data that may
be sent by the initiator, the level of error recovery supported, and whether or
not digests will be used for error detection. After both sides are satisfied with
the authentication and the setting of the operational settings, the target sends aLogin Responds PDU with an indication that the login procedure has
completed. Only then may the connection be used to pass SCSI commands and
data.
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NAMING
Borrowing from other Internet protocols, iSCSI use an URL-like
scheme to name targets. ISCSI names are meant to be global, similar to World
Wide Names used by Fibre Channel. An iSCSI entity might have its IP address
changed while retaining its name. An iSCSI entity is therefore identified by its
name and not its address. This allows for easier handling of iSCSI names by
proxies, gateways, network address translation boxes, firewalls, and so on.
iSCSI names should be unique worldwide. Typical iSCSI names might look
like this:
Iqn.2001-04.com.acme:storage.disk2.sys1.xyz
DISCOVERY
When using storage devices over a network, one has to deal with
the ability of an initiator to discover the devices it may use. One approach is
for an administrator to statically configure the initiator, providing the initiator
with a list of names and addresses of the iSCSI devices to which the initiator
may connect. If additional iSCSI devices were later added to the network, the
statically configured initiator would not be able to access the new devices
without being reconfigured. An alternative more dynamic method is to use
SLP, which already exists in the IP family of protocols. iSCSI targets can beadded to the network, and the topology can change over time, but initiators can
easily find new targets without having to be reconfigured. A similar
mechanism is provided by the recently defined iSNS protocol.
An additional discovery mechanism, Send Targets, is provided in
the iSCSI protocol itself, especially useful for gateway devices. In this method,
an initiator is statically configured to connect to specific iSCSI gateway
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devices. The initiator establishes a discovery session with the iSCSI gateway
device then responds with a list of attached iSCSI targets that are available to
the initiator. The initiator may then proceed to connect to the specified iSCSI
target devices.
DATA INTEGRITY
TCP has a checksum facility to help detect errors that occur
during transmission. While the probability of the TCP checksum failing to
detect an error is quite small, it is not good enough for some storage
environments. The TCP checksum also does not provide protection for
corruptions that occur while a message is in the memory of some router. iSCSI
therefore defines its own cyclic redundancy check (CRC) checksum to ensure
end-to-end integrity of its packet headers and data. Initiators and targets may
negotiate whether or not to use this CRC checksum.
SECURITY
When storage devices were directly attached to host machines, the
data on the storage devices was considered secure by its being inaccessible to
the outside world. With iSCSI attached storage devices, this is no longer the
case. A serious security problem may arise if sensitive storage data is accessed
over a general data network. One possible solution is to use a physicallyseparate network for the storage data, similar to what is done with Fibre
Channel (Fig.2. This solution requires a second physical IP network which is
still cheaper than having a second physical Fibre Channel network.
Alternatively, a single physical IP network can be used to get with encryption
of the storage data. Encryption of data on an IP network can be provided with
IPSec. iSCSI simply uses the existing IP-faulty security protocol to protect
sensitive storage data from possible security attacks such as spoofing.
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ANTICIPATED USE OF iSCSI
Some of the design decisions of iSCSI were strongly influenced
by the perception of how iSCSI would eventually be used. ISCSI was designed
to allow efficient hardware and software implementations to access I/O
devices attached over any IP network. iSCSI was designed for a wide variety
of environments and applications including local and remote storage access,
local and remote mirroring, local and remote backup/restore. It was assumed
that TCP/IP acceleration adapters and even iSCSI host bus adapters (HBAs)
would become prevalent, and would be strongly desirable to defend he
protocol to allow high-performance adapter implementations Mechanisms
were therefore included to overcome various anticipated problems, such as
maintaining high bandwidth frequently dropped packets. Care was taken to not
limit the application of iSCSI to disks; mechanisms were provided for various
types of SCSI devices, especially tapes, for which it is inconvenient and
perhaps prohibitive to cancel a restart commands.
DIRECT DATA PLACEMENT
In typical TCP implementations, data that arrive on a TCP
connection is first copied into temporary buffers. The TCP driver then
examines the connection identification information (source and destinationaddress and port numbers) determine the intended receiver of the data. The
data is then copied into the receivers buffer. For SCSI data, there might be
many pending SCSI commands at any given instant, and the received data
typically mist be copied into the specific buffer provided by the SCSI layer for
the particular command. This entire procedure might require the receiving host
to copy the data a number of times before the data ends up in the final
destination buffer. Such copies require significant amount of CPU and memory
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buffer usage that would adversely affect the system performance. It is
therefore most desirable to the able to place the data in its final destination
with a minimum number of copies.
iSCSI Data PDU headers contain sufficient information allow an
iSCSI adapter (HBA) perform direct data placement. The information provided
in an iSCSI Data PDU header include a transfer tag to identify the SCSI
command and its corresponding buffer, a byte offset relative the beginning of
the corresponding buffer, and the data length parameter indicating the number
of bytes being transferred in the current data packet. This information is
sufficient to enable direct placement of the arriving data into pre registered
SCSI-provided buffers. An iSCSI adapter then performs both TCP and iSCSI
processing on the adapter will have sufficient information in the TCP and
iSCSI headers to place arriving iSCSI data directly into the appropriate SCSI
buffers without having to copy the data into additional temporary buffers on
the host machine.
RECOVERY
The iSCSI protocol defines several levels of recovery to provide
resilience in the face of a wide range of possible errors and failures. iSCSI
handling and recovery is expected a rare occurrence, and may involve a
significant amount of overhead. It is anticipated that most computingenvironments will not need all the levels of recovery defined in the iSCSI
specification.
The most basic recovery class is session failure recovery. All
iSCSI specification complaint implementations must implement session failure
recovery. Session recovery involves the closing of all of the sessions TCP
connections aborting all outstanding SCSI commands on that session,
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terminating all such aborted SCSI commands with an appropriate SCSI service
response at the initiator and the restarting a new set of TCP connections for the
particular session. Implementations may perform session failure recovery for
any iSCSI error detected.
A less drastic kind of recovery implementations may perform its
digest failure recovery. If a CRC checksum error is detected on iSCSI data, the
data packet must be discarded. Instead of performing session recovery,
implementations may use the digest failure recovery mechanism to ask the
connecting peer to resent only the missing data. Similarly, if a sequence
reception timeout occurs, a similar mechanism can be used to ask the
connecting peer to resent the missing commands, responses or other number
packets that are expected.
If a CRC checksum error is detected on an iSCSI packet header,
the packet must be discarded since it was corrupted. As a result,
synchronization between the initiator and target may be lost. The iSCSI
protocol allows for a new TCP connection to be established within the session,
and defines mechanisms for the initiator and target to synchronize with one
another to continue to smoothly interact. A new TCP connection may be
designated to take over from an old TCP connection that seems to have
become defective. This level of recovery is called connection recovery.
Processing of commands that were started on the defective TCP connection
can be continued on the new TCP connection.
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UNDERSTANDING END SYSTEMS
An iSCSI environment can leverage existing IP networks; a
significant portion of the overall solution involves iSCSI end systems. Fig.8
outlines the significant functions of traditional IP Network Interface Cards,
traditional Storage Adapters, and new IP Storage Adapters.
Fig.8 Network Interface Cards and Host Bus Adapters
Network Interface Cards (NICs)
Traditional NICs (Ethernet adapters in servers and PCs) are
designed to transfer packetized file level data among PCs, servers and storage
devices, such as NAS appliances. However, NICs do not traditionally transfer
block level data, which is handled by a storage host bus adapter, such as Fibre
Channel or parallel SCSI. In order for a NIC to process block level data the
data needs to be placed into a TCP/IP packet before being send over the IP
network. Through the use of iSCSI drivers on the host or server, a NIC can
transmit packets of block level data over an IP network. When using an NIC,
the server handles the packet creation of block level data and performs all of
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the TCP/IP processing. This is extremely CPU intensive and lowers the overall
server performance. The TCP/IP processing performance bottleneck has been
the driving force behind the development of TCP/IP offload engines (TOE) on
adapter cards. A TOE removes TCP/IP processing from the host CPU and
completes TCP/IP processing and packet creation on the HBA. Thus a TCP/IP
offload storage NIC operates more like a storage HBA rather than a standard
NIC.
Storage Host Bus Adapters (HBAs)
Unlike NICs, Storage HBAs are designed to transmit block level
data to and from storage applications. A reference to the entire block is
transferred from the application to the adapter, bypassing the need to bread the
bloke into smaller frames; a process that takes place through a set of
specialized chips that enable the HBA to relieve the computer resources of the
CPU for this process. When it completes the task, the HBA forwards the
frames.
ISCSI ADAPTERS
iSCSI Adapters combine the functions of NICs with the function
of storage HBA. These adapters take the data in block form, handle the
segmentation and processing on the adapter card with TCP/IP processing
engines, and then send the IP packets across an IP network. The
implementation of these functions enables users to create an IP based SAN
without lowering the performance of the server. In advance of the introduction
of iSCSI adapters, some vendors released software versions of these adapters.
These software-enabled adapters accept block level data from applications, but
still require CPU cycles for the TCP/IP processing. The advantage of such
adapters is that they can work on existing Ethernet NICs. The main
disadvantage is that they require heavy CPU utilization for TCP/IP processing.
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DEPLOYMENT SCENARIOS FOR ISCSI
BUILDING NEW NATIVE ISCSI STORAGE NETWORKS
DATA CENTER APPROACH
An iSCSI SAN is a perfect choice for a user interested in moving
to networked storage. Using the same block level SCSI commands as direct
attach storage, iSCSI provides compatibility with user applications such as file
systems, databases, and web serving. Similarly, since iSCSI runs on ubiquitous
and familiar IP networks, there is no need to learn a new networking
infrastructure to realize SAN benefits. To build an iSCSI storage network in a
data center, iSCSI host bus adapters can be used in servers, along with iSCSI
storage devices and a combination of IP and Ethernet switches. IP Storage
switches and routers can be used if required. Fig.8 shows aprimary data center
iSCSI storage network connecting to remote sites.
Fig.9 Data Center iSCSI Storage Networks Offer Seamless MAN/WAN Access
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EXPANDING ISCSI STORAGE NETWORKS TO METRO AND WIDE
AREA NETWORKS
The rapid adoption and expansion of IP data on the Internet has proves
the viability of using IP across long distance wide area networks. Although it
is expected that initial deployments of iSCSI will use private networks, the use
of IPs security infrastructure (such as IPSes and SSL to provide authentication
and privacy) it will be possible to use public networks for wide area iSCSI
storage traffic as well.
APPLICATIONS FOR NATIVE ISCSI STORAGE NETWORKS
With native iSCSI storage networks customers can benefit from the
following applications in the data center:
(1)Server and storage consolidation
With a networked storage infrastructure, customers can link
multiple storage devices to multiple servers allowing for better resource
utilization, ease of storage management and simpler expansion of the storage
infrastructure.
(2)Accelerated Backup OperationsBackup operations previously restricted to operating across
traditional IP LANs at the file level can now operate across IP Storage
networks at the block level. This shift facilitates faster backup times, and
provides customers the flexibility to use shared or dedicated IP networks for
storage operations.
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(3)Seamless Remote Site Access and Storage Outsourcing
With the storage network based on IP, customers can easilyenable remote access to secondary sites across metropolitan or wide area IP
networks. The remote sites can be used for off-state backup, clustering or
mirroring/replication. Additionally, customers can choose to link to storage
service providers for storage outsourcing applications such as storage-on-
demand
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LINKING SANs WITH iSCSI
The iSCSI protocol is ideal for linking SANs over MAN and
WAN environments wince it uses TCP/IP as the transport. This includes
extending native iSCSI SANs and Fibre Channel SANs across a wide area
network. iSCSI SANs can be connected over a wide area network with
standard Ethernet equipment. When connecting to Fiber Channel SANs, an IP
Storage Switch is needed to convert the FC protocol to iSCSI.
IP Storage routers can bridge FC to iSCSI, while IP storage
switches bridge FC to iSCSI and provide added switching functionality. That
functionality, when provided in an IP Storage switch, allows users to perform
FC-to-FC switching, FC-to-iSCSI switching, or FC-to-Gigabit Ethernet
switching and Gigabit Ethernet to Gigabit Ethernet switching. Both IP storage
routers and switches allow users to extend the reach of the FC SAN and bridge
FC SANs to iSCSI SANs. Fig.10 shows a sample configuration based on IP
storage routers and switches.
Fig.10 Linking iSCSI to Fibre Channel
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Fig.(11)
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APPLICATIONS FOR LINKING ISCSI TO FIBRE
CHANNEL
IP Access to Storage/Storage Consolidation
Using iSCSI Adapters in servers, customers can now provide
access to FC storage resources across an IP network. This greatly expands
storage access flexibility, allowing customers to consolidate FC storage
without limiting access to servers. Database information, for example, can be
directly accessed from servers across an IP network.
Remote Backup for Enterprise Customers
With the ability to use IP networks, the combination of iSCSI and
IP Storage routers or switches enables remote backup for enterprise customers.
Remote sites can operate independently, yet still benefit from enterprise
storage resources for iSCSI server to FC storage backup and recovery. This
application allows data center managers to centralize corporate data resources
in one location while providing sophisticated enterprise storage management to
several remote customers at different sites.
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DEPLOYMENT EXAMPLES
Network Storage Services via iSCSI
Two iSCSI HBAs can be used in conjunction with standard Ethernet
NICs through a Gigabit-capable switch connected to an iSCSI-capable RAID
Array (Figure12). This configuration is appropriate as either the next step in
transitioning to an iSCSI-exclusive SAN or as an initial iSCSI SAN
configuration.
Fig.12 Network Storage Services via iSCSI
Multiple Cards to Single iSCSI Router
Multiple HBAs in separate servers can be used in conjunction
with a Gigabit capable switch connected to an iSCSI capable router with Fibre
Channel ports. This is then connected directly to a native Fibre Channel RAID
Array (Figure 13). This configuration is appropriate as the next step in
transitioning to an iSCSI front-end SAN with Fibre Channel storage devices.
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Fig.13 Multiple Cards to Single iSCSI Router
iSCSI HBA and Fibre Channel Tape Backup
An iSCSI HBA can be used in conjunction with a Gigabit-capable
switch connected to an iSCSI-capable router with Fibre Channel ports
connected to a Fibre Channel tape drive (Figure 14). This configuration can be
used as a means to perform backup and recovery using existing Ethernet
infrastructure.
Fig.14 iSCSI HBA and Fibre Channel Backup
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CONCLUSION
The iSCSI protocol enables access to storage devices over an IP
network. One of the main objectives in defining the iSCSI protocol was to
make use of existing IP infrastructure whenever possible. Thus, TCP is used as
the underlying transport, IPSec is exploited to provide network security, SLP
can be used to provide discovery, and so on. Since iSCSI runs over standard
off-the-shelf network compoens, the cost of setin up an iSCSI SAN is
significantly lower than that of a Fibre Channel SAN. This will make iSCSI
more affordable and manageable than Fibre Channel, and enable it to become
the protocol of choice for SANs. iSCSI will expand the market for networked
storage by giving IT managers another alternative to direct attached storage
that delivers the advantages of networked storage. IP storage networks take
advantage of IP networking knowledge in IT departments and use existing
network management and tools for LANs, MANs and WANs today. Riding the
IP wave of technology develoment and enhancements like the introduction of
10 Gigabit Ethernet, iSCSI provides a logical unified infrastructure
development path for corporations and service providers alike.
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REFERENCES
Features of iSCSI Protocol, Kalman. Z. Meth and Julian Satran, IBMHaifa Research Lab, IEEE Communication MagazineAugust 2003.
Performance Study of iSCSI-Based Storage Subsystems, Yingping Luand David. H. C. Du, University of Minnesota, IEEE Communication
MagazineAugust 2003.
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ACKNOWLEDGEMENT
I extend my sincere thanks to Prof. P.V.Abdul Hameed, Head of
the Department for providing me with the guidance and facilities for the
Seminar.
I express my sincere gratitude to Seminar coordinator Mr. Manoj K,Staff in charge, for his cooperation and guidance for preparing and presenting
this seminar.
I also extend my sincere thanks to all other faculty members of
Electronics and Communication Department and my friends for their support
and encouragement.
Sreeraj. K.P
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CONTENTS
INTRODUCTION ELEMENTS OF IP STORAGE FACTORS ENABLING IP STORAGE LEVERAGING THE BEST FROM STORAGE AND NETWORKING ADVANTAGES OF IP STORAGE ELEMENTS OF IP STORAGE NETWORKING ISCSI DEFINED BEBEFITS OF ISCSI WHO CAN USE IT ISCSI FEATURES
TCP
SESSIONS
ISCSI PROTOCOL DATA UNITS
LOGIN
NAMING
DISCOVERY
DATA INTEGRITY
SECURITY
ANTICIPATED USE OF ISCSI
DIRECT DATA PLACEMENT
RECOVERY
UNDERSTANDING END SYSTEMS DEPLOYMENT SCENARIOS FOR ISCSI APPLICATIONS FOR LINKING ISCSI TO FIBRE CHANNEL DEPLOYMENT EXAMPLES CONCLUSION REFERENCES
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ABSTRACT
In a world where Internet Protocol (IP) dominates local and
wide area networks, the data storage requirements grow unabated; it seems
inevitable that these two forces converge. The Internet Small Computer
Systems Interface (iSCSI) protocol unites storage and IP networking. iSCSI
enables the transport of block-level storage traffic over IP networks. It builds
on two widely used technologies - SCSI commands for storage traffic over IP
networks. It builds on two widely used technologies - SCSI commands for
storage and IP protocols for networking. iSCSI is an end-to-end protocol for
transporting storage I/O block data over an IP network. The protocol is used on
servers (initiators), storage devices (targets), and protocol transfer gateway
devices. iSCSI uses standard Ethernet switches and routers to move the data
from server to storage. It also enables IP and Ethernet infrastructure to be used
for expanding access to SAN storage and extending SAN storage and
extending SAN connectivity across any distance. This paper presents general
overview of iSCSI, outlining its introduction, details of the protocol, its
features, user benefits, and several typical deployment scenarios and
applications.