SAN for freshers!

Beginners Post!

Introduction:
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In today’s world, every thing is digital (files, songs, movies, photos, etc.) and our storage requirement is growing every day. In 2013 data is expected to reach 3.5 zetta bytes, up 48 percent from 2012. It is very clear that, demand for storage devices (Optical disks, HDD, SSD, Flash drives) is growing.



With this heavy demand and growing requirement it is very necessary for us to design a most efficient network that can provide an optimal enterprise solution which is highly compatible to deploy on current LAN and WAN technologies and allows to transfer bulk data over network providing high performance, scalability, security, availability along with more sophisticated and complete network management solution.

To satisfy these needs engineers came with different ideas, they are SAN (Storage Area Network), NAS (Network Attached Storage). Today we will briefly discuss the overview of SAN and its components.

SAN (Storage Area Network):
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SAN is similar to LAN (Local Area Network), except the fact that SAN handles large data transfers with the use of Fiber Channel interconnection technology. Fiber Channel (FC) is a high speed network technology that runs on high-speed optical fiber cables and serial copper cables. The FC technology was created to meet the demand for increased speeds of data transfer among computers, servers, and storage subsystems. Latest FC implementations of 20GFC offers throughput of 5100 MB/s (raw bit rates of 21.04 MB/s). Also a single FC network can accommodate up to 15 million nodes.

SAN carries data between servers (hosts) and storage devices through FC switches, this allows storage to be shared across multiple servers. As the organizations experiencing an explosive growth in information, the need to store, protect, optimize and manage efficiently. SAN meets all the above demands by providing physical communication infrastructure and enables secure and robust communication between hosts and storage devices.

SAN provides the flexibility of having a local network as well as it connects geographically dispersed servers and storage over WAN using ATM or SONET. Most importantly we use two most popular protocols iSCSI and FCIP to extend block-level access to applications over IP. Provided these sophisticated protocols and infrastructure SAN supports disk mirroring, backup and restore, archival and retrieval of archived data, data migrations (local or remote) between storage arrays.

Most importantly, SAN does not provide file-abstractions, only block-level operations are possible. However, file systems built on top of SAN’s do provide file-level access, and are known as SAN filesystems.


Components of SAN:
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The four most important components of SAN are:
1. Node Ports (N_Port) on servers (hosts)
2. Infrastructure (cabling, FC switches)
3. Storage arrays
4. SAN software

Node Port (N_Port): A port on a network node (host or storage) used in FC point-to-point or FC switched fabric topologies. There are several types of node ports, which are used to connect equipment to the fabric in FC nodes.

Fabric Port (F_Port): Port on FC switch to connect to any node in FC network E_Port: Connection between two FC switches (ISL’s)

N_Port is seen on the Host-bus Adapter (HBA). The major manufacturers of HBA’s are Qlogic and Emulex.

Infrastructure:
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This plays a major role in the SAN environment, it provides physical connectivity between host and storage array. The two major components are cabling and FC switches. Cables can be multi-mode optical fiber or single-mode optical fiber. FC fabric is a core component of SAN, as SAN is completely based on FC network only FC switches are compatible with the Fiber Channel Protocol (FCP). Fabric is a network of fiber channel devices which allows many-to-many communications.

Major manufacturers of FC switches: Brocade, Cisco.

Storage Arrays:
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A storage array or a disk array is a disk storage which contains multiple disk drives. An intelligent storage array contain Front-End, Cache, Back-End, physical disks.

Major manufacturers of Storage Arrays are: EMC, NetApp, Hitachi, IBM, HP, Dell