RAID, NAS and SAN are key concepts when you coming to storage in IT. As an IT Architect that you should know what each stands for and how and where to use this.

Know About RAID:

RAID stands for Redundant Array of Independent Disk at storage level and there are 10 types of RAID available.

Type of RAID starts from RAID 0, 1, 2,3,4,5,6... and 10.

We need RAID at storage level to handle storage and aspect of Speed, Fault Tolerance and Redundancy.

RAID-0 will read and write data into two disk. If one of disk fails then the data can't be retrieved. RAID-0 is very useful if we are consider the performance factor alone. This RAID-0 is not advisable if your need is on reliability.

RAID-1 will read and write data between two disk as disk copy/mirroring way. Its duplicate whole data between disk-0 and disk 1. In case of disk-0 fail then the whole data can be retrieved from disk-1. This options provide data reliability and fault tolerance but speed wise not advisable. Most of the corporates use RAID-1 storage.

RAID2 uses the Error correction technique which you need minimum of 4 disk for data writing and 3 disk for error correction. This not commonly used at corporates. At this moment no body uses in the infra design.

RAID 2-4 uses the parity bit at block level but this approach also not commonly used.

RAID-5 is used with distributed parity bit at block level and the data storage and parity bit is distributed across the disk. So the data failure, data recovery and data storage was optimum utilization. Most of the corporates use this approach in their storage when comes to High Availability.

RAID-10 is the hybrid approach between RAID-0 and RAID-1 in storage design. Which provides the fast data retrieval and fault tolerance. This is very suites for mission critical applications and expensive in-nature.

Know About NAS:

NAS stands for Network attached storage which is traditionally called as File Server. This approach most of the small and medium sized organization uses to store and retrieve their documents.

When you position your server (web,app or DB) then NAS will be mounted as external storage as dedicated file server. This will be used store files, install OS and backup those files at infra layer.

Servers will access this NAS over (eg: NASshare etc)
Servers and NAS devices are connected over Network Switch (ex: iSCSI).

Know About SAN:
SAN stands for Storage Area network which is an advanced storage technique available in industry. This SAN store the data in block level and mounted with your servers as an accessible external drive via network switch.(ex: Server will access this SAN over D:SANshare etc)

Benefit SAN is to provide the flexibility on optimum storage utilization and logical/virtual storage allocation at runtime. It means the virtualization technique has been applied in storage using SAN Devices. These storage blocks are called as LUNS (Logical units).

LUNS are allocated to different servers from the same SAN. This provide dynamic storage allocation each servers dynamically which saves the organizational data storage cast and reduce the wastage on storage device non-utilization which traditionally we do it in fileserver or physical mounted external hard disk.

Servers (Web,App,db) are connected to SAN devices via Network switch. This Network switch has two types of connectivity for SAN.

Type 1 is connected via iFC ( Fibber channel) and Type 2 is connected via iSCSI (traditional switch device).

Always suggest to store the mission critical data either in RAID-1 or 5 or 10 / SAN .

About Author / Additional Info:
Arivuvel Ramu,
Sr. Architect