SAN Overview

Storage Area Network solutions (SANs) are quickly catching on as one of the best ways to optimize storage space in a network.  Daly, a Maryland-based value-added reseller, has over 16 years of experience working with the latest technology solutions, most recently SANs.

Already a popular solution for many companies and government agencies, Daly offers its customers personalized SAN configurations to suit the specific needs of any business.  The first step is to decide if a SAN solution is the ideal choice for the individual.

With today’s servers growing smaller every year, the amount of internal storage they are able to hold is decreasing.  This change is bringing about the need for fast, scalable external storage solutions for the servers of today and tomorrow.  Although external storage is not a new concept, a single storage cabinet with the ability to serve a heterogeneous network infrastructure and provide centralized management and security is an enhancement to any network.

Storage Area Networks centralize storage, administration, replication and protection from a single location making them an attractive solution to the overwhelmed network administrator.  With all the problems and updates, including hardware and software, that a support staff has to deal with throughout the day, he or she cannot be worried about the restrictions and concerns of a lack of disk space.  Both network administrators and the users they support are affected by the constraints of storage.  Storage Area Networks help to alleviate this problem.   Storage Area Networks are designed to assign data backup and restore functions to a secondary network where they can perform their tasks without interfering with the functions and capabilities of the server.

By definition, a SAN (Storage Area Network) is at least two devices, a host and a subsystem, connected by at least one switch or hub.

Although this is a broad definition, it helps define the basic SAN function.  SANs connect devices through a network of switches, hubs, routers and servers to facilitate the transmission of raw blocks of data.  From these criteria, SANs can guarantee compelling advantages: storage consolidation, centralized management, improved data access, flexibility for growth, security, data movement overhead taken off the server and backup. 

A SAN is actually a fabric of components comprised of hubs, switches and gateways/routers used to connect storage devices.

Interfaces and Fibre Channel

Since storage devices require manufacture with an interface for accessing data that defines how data is transported, the interface defines the capabilities of the device.  There are three major types of interfaces manufactured on drives today:  IDE, SCSI and Fibre Channel.  IDE is designed as a simple, direct attached storage device.  SCSI was designed to be more robust, performance oriented, and indirectly attached.  Fibre Channel evolved from SCSI by focusing on easy attachment and offering a single wire or optical interface, creating an addressing system capable of millions of different direct connections.

Some confusion arises from Fibre Channel and SAN being used synonymously.  Fibre Channel is not a SAN, and a SAN is not Fibre Channel.  Fibre Channel is an enabling technology for SANs that allows a network to directly attach to a storage device and give direct block access to the network.

Currently, most SANs still perform backup operations through the server, even if Fibre Channel architecture is in place. The server reads from the disk array or RAID set (Redundant Array of Inexpensive Disks) and, once the data is received by the server, it then writes the backup to tape over the Fibre Channel interface.  This may require 25% or more of the server cycles to be dedicated to the backup operation.  As a result, backups cannot occur during peak business periods. This puts pressure on backup windows and when backups do occur, it is expensive to pay for the server cycles required.  As backup technologies evolve, however, the necessity to have a server, or servers, handling backup operations is diminishing as the reality of server-less backups begin to appear.  Numerous software manufacturers are now incorporating a means to move and control nearly every aspect of a backup operation away from the server and LAN to a SAN.

The Mechanics

With a SAN, computers have a high-bandwidth connection between each other and their disk storage.  Fibre Channel provides as much as 200 megabytes per second of bandwidth compared to 100BaseT Ethernet at about 5 megabytes per second.  Fibre Channel yields speeds up to 40 times faster than 100BaseT Ethernet.  SANs also have an added benefit of requiring substantially less processor power to transmit the same amount of data as a LAN (Local Area Network).  The purpose of LAN communication protocols is to use less-than-perfect connections and thus, the software contains a lot of error checking and rechecking that controls the data flow over the LAN.  SANs use disk media channels in order to provide hardware error checking systems, eliminating data transfers across the network and freeing up the processors.  While 100BaseT Ethernet could use 30% of the processing power of a typical computer to move some data at 5 megabytes per second, a SAN would use less than 5% of the same processor power to move the same data at nearly 100 megabytes per second.

Even though the SAN connects multiple computers to storage, some software is still required to make the SAN and the computers work together.  Unfortunately, the operating systems used on today's computers expect to have any storage accessible through their Host Bus Adapters (HBAs), available for their exclusive use.  Data on those disks will become scrambled should multiple computers be connected to the same disk volumes at the same time the SAN's hardware allows.  The easiest way to overcome this problem is to use what is generally referred to as LUN masking.  LUN masking allows a disk across a SAN to be assigned to one computer connected to the SAN and effectively hides or masks that disk from the view of the other computers.  If you use LUN masking, a single RAID set could be partitioned into multiple logical disks (LUNs), each of which is assigned to a specific computer.  While this would allow multiple computers in a facility to share a single RAID, it would not allow multiple computers to access all of the files on that set.

SAN Implementation 

The decision to implement a SAN is an issue that takes a lot of thought and premonition.  An initial evaluation of current servers, their storage space and the applications that reside on them is the first step.  Considerations begin with storage – how much is currently available to handle the daily load?  Are several servers doing the job function of one due to the lack of storage or the capability to increase it?

Determining factors for choosing SAN as the storage solution are: (1) the network storage is at a premium; (2) the client is looking for sizable room to grow and (3) storage must be consolidated due to heterogeneous server operating systems.  A SAN solution is also the best bet if there is a high need for data protection.

After determining to implement a SAN into a new or existing network, several aspects need to be evaluated and settled upon during the decision-making process.  Whether designing a new network or adding a SAN to an existing one, it is wise to apply careful thought and planning to the process of SAN implementation.  The current servers and storage of the network should be evaluated, as well as the applications and data that reside on them.  It is also a good idea to compose diagrams of how the servers are physically placed in relation to one another and how they see and use each other’s resources.

With the various options offered by Daly in the way of SANs, the configuration process will be different for every network. Daly ensures that individual needs are met by drawing up customized specifications for each client.

A few questions that will help Daly to configure the optimum SAN solution for the individual customer include:

1. How many servers are expected to be on the SAN?
2. Will new servers be purchased to access the SAN or will existing machines handle everything?
3. Is the amount of time reserved for completing backups getting smaller or non-existent?
4. How fast is the business or organization growing?
5. What is the level of protection that is needed?
6. Which is more important, speed or space? 

By answering these questions, Daly can develop the right solution for any business.  Daly puts together all of the parts, both hardware and software, necessary to meet the tailored specifications for the SAN.  The manufacturer then approves the entire list to guarantee compatibility and that nothing has been overlooked.  Depending upon the customer’s needs, Daly also develops a Statement of Work (SOW) detailing the installation and configuration of the SAN.  Daly then delivers and builds the SAN on-site, as well as makes all connections to the servers and backup devices as outlined in the SOW.

A few things are required of the customer interested in SAN implementation: (1) Ensuring that their site meets the power requirement needs of the SAN; (2) determining a suitable location for the assembly of the storage cabinet and placement of all related items including the fire switch/hub, backup devices and UPS’s; (3) designating a server into which any SAN related software may be installed; and (4) deciding disk stripes and storage allocations for each attached server. 

	The first step to implementing a SAN solution is an initial evaluation of current servers, their storage space and the applications that reside on them.  Considerations begin with storage – how much is currently available to handle the daily load?  Are several servers doing the job function of one due to the lack of storage or the capability to increase it?
	Determining factors for choosing SAN as the storage solution are: (1) The network storage is at a premium, (2) the client is looking for sizable room to grow and (3) storage must be consolidated due to heterogeneous server operating systems.  A SAN solution is also the best bet if there is a high need for data protection.
	Certain aspects must evaluated and settled upon after determining to implement a SAN into a new or existing network.  The current servers and storage of the network should be evaluated, as well as the applications and data that reside on them.
	The configuration process will be different for every network with the various SANs options offered by Daly. Daly guarantees to meet individual needs by drawing up customized specifications for each client.

To find out how Daly can help you with a Storage Area Network solution, please contact Daly Technical Services at (888) DALY-TEC or visit www.daly.com.