Database Essentials – Understanding SAN and its Advantages and Disadvantages

SAN or storage area network is an upgraded storage technology in which the storage is moved more effectively into the network than directly connected to the database storage servers. Here, we will check out SAN, how it functions, and the unit of storage as LUN, different storage protocols, and the advantages and disadvantages.

Storage Area Network

SAN is the short form of Storage Area Network, primarily a high-speed network with many interconnected storage devices.  The network is equipped with fiber switches and cables to connect database servers using SAN as a shared pool to store the data and filers.

In traditional data storage, each server consists of its dedicated drives located on the server. All the database files and application-related data are stored in these native drives. However, with the increase in the applications’ numbers and size, the native data drives started getting exhausted, and a need for more sophisticated storage mechanisms arose. For example, if an enterprise application is running on a shared server, then there is a chance that it may get exhausted soon, and there may not be any further space for hosting more websites.

So, the ideal solution is to think of adding more storage to the server. However, this will incur a higher cost and also may take more time to implement. Along with these, the free space you get is actually on another server, so you cannot fully use it. We may feel that there must be a pool of all the hard drives that a server can use in full or a portion.

Storage using SAN

In SAN-based storage, the storage space becomes shared, and it functions as an ideal pool or different segments of storage. A user may opt for basic storage initially based on the requirement and can easily scale up when needed dynamically by adding new hardware.

Concept of LUN

LUN is a standard that is expanded as a logical unit number. A particular LUN is assigned to all the devices. All the storage-related devices and application-specific devices execute the input/output functions with a unique logical unit number or LUN. For example, a computer uses the LUN to interact with a storage device specified by the SCSI (Small Computer System Interface). Here, SCSI works with the specifications related to data transportation between the storage devices and the services or applications using standard protocols like Internet SCSI or Fiber Channel, etc. In this model, the server which holds the data will have a SCSI client, and the storage will have a server or what is called a LUN. This LUN will identify the storage device of the collection of storage devices, which may also be a part of a large storage system in segments on the host computer. The administrator can assign the needed permissions to the users based on the specific LUNs as data access privileges as read-only, read, write, replace, delete, etc. For setting up SAN, you can coordinate with expert remote database administrators.

 Benefits of SAN

As we know the fundamental concepts of SAN and LUN, now let us look into the major benefits of SAN in enterprise database administration.

  • Centralize access: In SAN, the data and file storage is centralized, which makes it much easier to implement new structures and policies.
  • Ensuring a high-speed network: As we have seen above, the switches and cables used are the latest fiber optics and ensure optimum speed in terms of data transactions. The user computers will have the impression as the data is present locally and instantly accessible.
  • Quick recovery: As we can see, the processing servers and the storage of data and applications are effectively decoupled. If there is a failover as hardware failure or other shutdowns, then the data is still present and can be recovered. Once the server is reestablished, it can reload the data and start to function as normal.
  • Failover mechanism – When one server in the network fails, another alternate server in the SAN environment will take over the process and data requests. It can do automatic rerouting of the traffic and also ensure backup storage.
  • Scalability – Based on the user needs, one can add storage devices anytime to the SAN environment if the applications need more capacity. Easy any-time scalability also makes SAN more cost-effective.
  • Security –  In terms of security, you can customize the security levels to various users as SAN offers user-based access to the storage. Only authorized persons can access the storage, and the read, edit, and delete privileges can also be restricted to the concerned users. This will help ensure optimum safety of the data and application-related aspects.

Drawbacks of SAN

Along with the advantages of SAN, as we discussed above, it will be ideal to know some disadvantages of the same. The initial thing noted is the cost. Even though the running cost and the cost of scaling are lesser than the conventional mode of storage, the initial set up cost of SAN may be far higher than the other.

Cloud computing with SAN

As of late, there is an increasing number of businesses using cloud storage. Cloud services can only be used for just storage. Many providers are offering such services. With the cloud, the users can choose only minimally required storage initially, and the latter scale it up based on the requirement. The catch here that you have to pay only for what you use. SAN and cloud-based storage’s major difference is that SAN still exists as local to an enterprise in which the servers are linked to the storage with high-speed fiber-optic switches.  Cloud storage, on the other hand, is connected through the internet, so there may be latency, and also, you do not know where your data is located.

For those who want to leverage the benefits of both, it is also possible for an enterprise to choose a hybrid model where the less critical storage can be done on the cloud, and the most critical data store can be built on SAN locally.