10.Storage

CNIT 24200 - Storage Technology

  • Instructor: Robert Deadman, PhD

  • Institution: Purdue Polytechnic

Overview of Storage Types

Objectives for Storage Lectures

  • Differentiate between:

    • NAS (Network Attached Storage) and SAN (Storage Area Network)

    • Block devices and File Containers

    • Solid State Drives (SSD) and Magnetic/Mechanical Hard Drives

    • Interconnections for hard drives

    • RAID levels and reasons to use each.

Block Devices vs. File Containers

Block Devices

  • Characteristics:

    • Physical devices (e.g., Hard Drives)

    • Must be partitioned and formatted before data storage.

  • Formatting results in a file system (e.g., NTFS).

    • Example: Block Device File Container created for NTFS.

File Containers

  • Characteristics:

    • Logical devices formed within the partitions of block devices.

    • Unallocated space is secondary storage.

Types of Storage

  • Magnetic Hard Disk

  • Solid State Drives:

    • Two types: Flash drives and SSDs.

  • Optical Drives (e.g., CD, DVD, Blu-Ray)

  • RAID Arrays:

    • Hardware and Software implementations.

  • Storage Area Networks:

    • Types include Fibre Channel, iSCSI, etc.

Internal Components of Hard Drives

Key Components

  • Base Casting, Spindle, Slider (and Head), Actuator Arm, Cover, Platters.

  • Connector for the logic board.

  • Dust and smoke particles are concerns for drive performance.

Disk Structure

Disk Numbering and Tracking

  • Disks may be numbered starting from 0 or 1 depending on the OS.

  • Data is stored in concentric circles known as tracks, and sectors are the smallest units of storage.

  • Each sector contains 512 bytes of data.

    • Physical sectors start numbering from 1.

Cylinder, Head, and Sector (CHS) Concept

  • CHS gives a three-dimensional coordinate for data access.

  • Example: Cylinder 4, Head 4, Sector 4.

Clusters

  • Cluster characteristics:

    • Composed of multiple sectors (8 sectors per cluster).

    • Only one file can reside in a single cluster, leading to potential wasted space.

Logical Block Addressing (LBA)

  • Sectors addressed as a continuous stream.

  • LBA simplifies addressing by recurring numbers from the first physical sector.

File Systems

Characteristics of File Systems

  • Hierarchical organization of files and directories.

  • Varies according to OS and file system used.

    • Examples: FAT16, FAT32, NTFS, exFAT, etc.

  • Limitations include filename formats, maximum file sizes and directory limits.

Disk Partitioning Strategies

Partition Types

  • Each physical disk is broken into one or more partitions, which hold file systems.

  • Volume types:

    • Basic volumes include primary and extended partitions.

    • Dynamic disks can create various volume types (simple, spanned, striped, mirrored, RAID-5).

System Types

  • System Partition: Holds OS files necessary for booting.

  • Swap Partition: Reduces fragmentation of the swap file.

  • Data Partition: Optional separation of user data.

Master Boot Record (MBR)

  • The boot sequence starts from MBR, located in the boot sector just before partition data.

  • Non-active primary partitions stored in Extended Boot Records (EBR).

  • MBR importance in system stability and recovery.

RAID Configurations

Types of RAID Levels

  • RAID 0: Data striping without redundancy.

  • RAID 1: Data mirroring for fault tolerance.

  • RAID 5: Data striping with parity for redundancy.

  • RAID 10: Combination of striping and mirroring for performance and fault tolerance.

Storage Networking Types

NAS vs. SAN

  • NAS: File-level storage accessible over a network, requiring less dedicated hardware.

  • SAN: Block-level storage, using dedicated hardware and capable of higher transaction throughput.

iSCSI Protocol

  • Allows SCSI commands to be sent over TCP/IP.

  • Supports file sharing via dedicated initiators and targets.

  • Implementations include naming conventions and security via authentication protocols.