Introduction

Volatility

• Volatile - Volatile data is lost when the power of the device is switched off
• Non-Volatile - non-volatile information persists even after the device is switched off

Storage Factors

• Speed of data access
• Cost of data storage
• Reliability of data retrieval

Storage Hierarchy

• Primary - storage is the fastest. It is also volatile. Primary data sources include the cache and the main memory.
• Secondary - storage includes non-volatile on-line storage. It includes flash memory and magnetic (HDD) discs.
• Tertiary - storage is off-line and used for archival. It is non-volatile. It has a slow access time. It includes magnetic tapes and optical storage.

Interaction Interfaces

• SATA - Serial ATA - supports data transfer of up to 6 Gb/s
• SAS - Serial Attached SCSI - supports upto 12 Gb/s
• NVMe - Non-Volatile Memory Express - supports up to 24 Gb/s

Storage Interfaces

• SAN - Storage Area Network - a large number of disks connected to servers by a high-speed network.
• NAS - Network Attached Storage - a networked storage that provides a file using networked file system protocol rather than a disc interface.