Disk Subsystem - Storage Basics-2

In storage, the directly connected small disks are replaced by large storage subsystems connected via storage network.  It has the flexibility to assigned hard disk to the servers as per the availability. Servers are either connected to Disk subsystem directly or indirectly via SAN ( storage Area Network).

There are below advantages of using storage system.

1. High Availability:- Data will remain available if any of the disk fails. With the help of RAID configuration we can provide 100% data backup and fault tolerance.

2. High performance:-  All the disk are available to the servers and they can get the hard disk as and when they need it.

3. Instant Copy: - Controllers are responsible to perform the parallel write of data to multiple disks to increase the write speed.

4. Remote mirroring:- RAID controllers are available to provide high fault tolerance by copying the data to multiple disks.

Disk Subsystem:-  It consists of storage devices like Hard Disks, Tapes and Controllers. There can be a disk subsystem where controller is not present.

 JBOD (Just bunch of Disk) is the low cost storage subsystem in which all the disks are placed in single enclosure with common power supply. There is no controller present in JBOD. It is used for small deployments.

Components of Disk Subsystem-

•   Storage Devices: - Hard disk and tapes are used to store data and to increase the fault tolerance we may need the controller to handle the individual disks.

•     Controllers: - It’s like brain of the complete disk subsystem and makes the entire cluster of small disks as one big virtual disk. RAID (Redundant Array of independent disks) Controllers controls the disks subsystem and provide instant copy and remote mirroring features to provide high fault tolerance.

It is responsibility of the controller to store data to the hard disks.