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NAS / SAN
NAS – Network Attached Storage (Filer)
SAN – Storage Area Network
What differentiates the two?
NAS
What is a NAS?
Network attached storage (NAS) is an adding of
disk drives and PC servers to existing networks
to increase storage space.
NAS appliances expand storage capacity
independently of the PC server and provide a
simple, cost-effective solution to adding
network storage.
What components make up a NAS?
Appliance, disk storage, network connection
NAS
What is a NAS appliance?
NAS appliances were developed as an alternative to
the general-purpose server solely for file storage.
They are single-purpose appliances dedicated to
serving files that provide a flexible and inexpensive
alternative for adding storage to the workgroup.
NAS
NAS appliance hardware has been streamlined
by eliminating unnecessary components,
which results in significant cost savings over
general-purpose servers.
For example, unlike a PC server, a NAS
appliance has no need for a keyboard,
mouse, monitor, or I/O ports.
NAS
NAS appliances run a highly efficient operating
system, typically with built-in support for
multiple networking protocols, which has
been optimized for serving files on the
network.
Unlike traditional servers whose operating
systems charge a "per seat" licensing fee for
each user connected to the server, there are
no licensing fees with NAS appliances.
NAS
How does it communicate?
An appliance communicates using
Network File System (NFS) for
UNIX/Linux environments, Common
Internet File System (CIFS) for
Microsoft Windows environments, FTP,
http, and other networking protocols.
NAS
Applications for NAS
• File sharing and online storage.
• Backups
• Duplication of images for frequently used
software configurations for distribution.
• Increase online storage at particular
locations for remote offices.
NAS
Required/Desirable Features
• Compatibility with Existing Networks
• Easy Installation
• Intuitive Web Administration
• Network Security
• Cross-Platform File Sharing
(Cont.)
NAS
Legacy cross-platform environment
NAS
With NAS
NAS
Required/Desirable Features (Cont)
• Compatibility with Established Backup
Policy
• Improved Performance under Load
• High Reliability
• Portable Storage
NAS
Benefits
• With a NAS appliance, users anywhere on
the network—from corporate headquarters to
remote offices—are assured of timely, reliable
access to their data.
• NAS provides IT managers have a costeffective file server that is easily integrated
into an existing workgroup.
NAS / SAN
Similarities:
Both provide
• optimal consolidation.
• centralized data storage.
• efficient file access.
NAS / SAN
Similarities:
Both allow you to:
• share storage among a number of hosts
• support multiple different operating systems at the same time
• separate storage from the application server.
NAS / SAN
Similarities:
Both can
• provide high data availability
• ensure integrity with redundant components and
redundant array of independent disks (RAID).
NAS / SAN
Differences:
NAS and SAN represent two different
storage technologies and they attach to
your network in very different places.
NAS
NAS is a defined product that sits
between your application server and
your file system
SAN
SAN is a defined architecture that sits between a file
system and an underlying physical storage It is its
own network, connecting all storage and all servers.
NAS
NAS is network-centric.
NAS provides security and performs all file and
storage services through standard network
protocols, using TCP/IP for data transfer,
Ethernet and Gigabit Ethernet for media
access, and CIFS, http, and NFS for remote
file service.
SAN
A SAN is data-centric - a network dedicated to
storage of data. Unlike NAS, a SAN is
separate from the traditional LAN or
messaging network. Therefore, a SAN is able
to avoid standard network traffic, which often
inhibits performance.
SANs employ gateways, switches, and routers
to facilitate data movement between
heterogeneous server and storage
environments.
NAS / SAN
NAS is file oriented
SAN is SCSI block oriented
NAS is simple to install (Plug and Play)
SAN is complex
SAN
What is a SAN? A SAN consists of a
dedicated network that interconnects servers
and their applications to storage resources
with the use a switch or hub. (Hubs seldom
seen any more.)
Storage resources usually consists of disks
and tapes.
The dedicated network is usually fibre
channel or iSCSI
SAN
An adapter card on the server is connected
by fiber optic or copper cabling to a SAN
switch.
Disk arrays and tape devices are also
connected to the switch, which brings all
servers and storage devices into a peer-topeer network.
SAN
NAS
NAS
NAS
NAS
SAN
SAN
SAN
How can SAN accommodate a mixed
computing environment (UNIX,
WINDOWS, NOVELL)?
Through a technique called zoning.
SAN
SAN
A method of subdividing a storage area
network into disjoint zones, or subsets
of nodes on the network. Storage area
network nodes outside a zone are
invisible to nodes within the zone.
Moreover, with switched SANs, traffic
within each zone may be physically
isolated from traffic outside the zone.
SAN
What type of network access does SAN
employ?
Fibre channel
iSCSI
Infiniband
CIM (Common Information Model)
Bluefin (based on CIM)
Fibre Channel
What is fibre channel?
Fibre channel is a high performance serial link
supporting its own, as well as higher level
protocols such as the FDDI, SCSI, HIPPI and IPI
It is neither a fiber or a channel.
Fibre Channel is the general name of an integrated
set of standards developed by the American
National Standards Institute (ANSI).
Fibre Channel
What is a channel?
There are two basic types of data
communication between processors and
between processors and peripherials:
channels and networks.
.
A channel provides a direct or switched point-topoint connection between the communicating
devices.
A channel is typically hardware-intensive and
transports data at the high speed with low
overhead.
Fibre Channel
A network is an aggregation of distributed
nodes (like workstations, file servers or
peripherials) with it's own protocol that
supports interaction among these nodes.
Fibre Channel
A network is an aggregation of distributed
nodes (like workstations, file servers or
peripherials) with it's own protocol that
supports interaction among these nodes.
Networks can handle a more extensive range of
tasks than channels as they operate in an
environment of unanticipated connections,
while channels operate amongst only a few
devices with predefined addresses.
Fibre Channel
Fibre Channel attempts to combine the best of
these two methods of communication into a
new I/O interface that meets the needs of
channel users and also network users.
It allows for an active intelligent interconnection
scheme, called a Fabric, to connect devices.
Fibre Channel
In Fibre Channel terms the switch connecting
the devices is called Fabric.
The link is the two unidirectional fibres
transmitting to opposite directions with their
associated transmitter and receiver.
Each fibre is attached to a transmitter of a port
at one end and a receiver of another port at
the other end.
Fibre Channel
When a Fabric is present in the configuration,
the fibre may attach to a node port (N_Port)
and to a port of the Fabric (F_Port).
Fibre Channel
FC is structured as a set of hierarchical
functions.
Fibre Channel
The lowest level (FC-0) defines the physical link
in the system, including the fibre, connectors,
optical and electrical parameters for a variety
of data rates.
(133 Mbit/s, 266 Mbit/s, 530 Mbit/s, and 1
Gbits/s) and on three types of both electrical
and optical media.
The system bit error rate (BER) at the
supported media and speeds is less than
10exp-12 [1].
Fibre Channel
FC-1 defines the transmission protocol
including serial encoding and decoding rules,
special characters and error control. The
information transmitted over a fibre is
encoded 8 bits at a time into a 10 bit
Transmission Character.
Fibre Channel
The Signaling Protocol (FC-2) level serves as the
transport mechanism of Fibre Channel. The
framing rules of the data to be transferred
between ports, the different mechanisms for
controlling the three service classes and the
means of managing the sequence of a data
transfer are defined by FC-2. To aid in the
transport of data across the link, the following
building blocks are defined by the standard:
• Ordered Set
• Frame
• Sequence
• Exchange
• Protocol
Fibre Channel
The Frame Header is used to control link applications, control
device protocol transfers, and detect missing or out of order
Frames. An optional header may contain further link control
information.
Fibre Channel
A maximum 2112 byte long field (payload) contains the
information to be transferred from a source N_Port to a
destination N_Port.
Fibre Channel
To ensure efficient transmission of different types
of traffic, FC defines three classes of service.
Class 1 is a service which provides dedicated
connections, in effect providing the equivalent of
a dedicated physical connection. Once
established, a Class 1 connection is retained and
guaranteed by the Fabric. This service
guarantees the maximum bandwidth between two
N_Ports, so this is the best for sustained, high
throughput transactions. In Class 1, Frames are
delivered to the destination Port in the same
order as they are transmitted. Figure 5 shows the
flow control management of a Class 1
connection.
Fibre Channel
Fibre Channel
Class 2 is a Frame-switched, connectionless service
that allows bandwidth to be shared by
multiplexing Frames from multiple sources onto
the same channel or channels. The Fabric may
not guarantee the order of the delivery and
Frames may be delivered out of order.
If delivery cannot be made due to congestion, a
Busy frame is returned and the sender tries
again.
Fibre Channel
Fibre Channel
• Class 3 service is identical to Class 2, except that
the Frame delivery is not confirmed. (Flow control
is managed only on buffer level) This type of
transfer, known as datagram provides the
quickest transmission by not sending
confirmation.
Fibre Channel
Fibre Channel
The FC-3 level of the FC standard is intended to
provide the common services required for
advanced features such as:
• Striping -To multiply bandwidth using multiple
N_ports in parallel to transmit a single information
unit across multiple links.
• Hunt groups - The ability for more than one Port
to respond to the same alias address. This
improves efficiency by decreasing the chance of
reaching a busy N_Port.
• Multicast - Multicast delivers a single
transmission to multiple destination ports. This
includes sending to all N_Ports on a Fabric
(broadcast) or to only a subset of the N_Ports on a
Fabric.
Fibre Channel
FC-4, the highest level in the FC structure
defines the application interfaces that can
execute over Fibre Channel. It specifies the
mapping rules of upper layer protocols
using the FC levels below
Three IP SAN Transports
The three IP storage networking transports are
significantly different, but they all provide a common
function: transporting block-level storage over an IP
network. All three transports enable end users to
• Leverage existing storage devices (SCSI and Fibre
Channel) and networking infrastructures (Gigabit
Ethernet);
• Maximize storage resources to be available to more
applications;
• Extend the geographical limitations of DAS and SAN
access;
• Use existing storage applications (backup, disaster
recovery, and mirroring) without modification; and
• Manage IP-based storage networks with existing tools
and IT expertise.
iSCSI
The Internet Small Computer Systems
Interface (iSCSI) protocol defines the
rules and processes to transmit and
receive block storage applications over
TCP/IP networks by encapsulating SCSI
commands into TCP and transporting
them over the network via IP.
FCIP
Fibre Channel over TCP/IP (FCIP) provides
a mechanism to "tunnel" Fibre Channel
over IP-based networks. This enables
the interconnection of Fibre Channel
SANs, with TCP/IP used as the
underlying wide-area transport to
provide congestion control and in-order
delivery of data.
iFCP
The Internet Fibre Channel Protocol (iFCP)
supports Fibre Channel Layer 4 FCP over
TCP/IP. It is a gateway-to-gateway
protocol where TCP/IP switching and
routing components complement and
enhance, or replace, the Fibre Channel
fabric.
iFCP
The Internet Fibre Channel Protocol (iFCP)
supports Fibre Channel Layer 4 FCP over
TCP/IP. It is a gateway-to-gateway
protocol where TCP/IP switching and
routing components complement and
enhance, or replace, the Fibre Channel
fabric.
iSCSI
iSCSI (Internet Small Computer System
Interface) is a TCP/IP-based protocol
for establishing and managing
connections between IP-based storage
devices, hosts and clients. SNIA - IP
Storage Forum: http://www.snia.org/
iSCSI describes:
• Transport protocol for SCSI which
operates on top of TCP
• New mechanism for encapsulating SCSI
commands on an IP network
• Protocol for a new generation of data
storage systems that natively use
TCP/IP
NAS / SAN
SAN