• Components of storage
• The hard disk types
• The disk inside
• Disk Arm Scheduling Algorithms

• Files
• Directories
• File systems
• Physical storage & Logical storage
• Logical Volume Manager (LVM)

• SATA :
  • SATA (Serial Advanced Technology Attachment)
  • 6GB/s
• SAS
  • SAS (Serial Attached SCSI)
  • SCSI (Small Computer System Interface)
  • 12GB/s
• 5400, 7200, 10000, 15000 RPM
• Cache: 8 ~ 256 MB
• SSD (Solid State Disk)

• An illustration of cylinder skew.
• CHS: Cylinder, Head, Sector
• CHS tuples can be mapped onto LBA (Logical Block Addressing) addresses

• (a) No interleaving.
• (b) Single interleaving.
• (c) Double interleaving.

• (a) Physical geometry of a disk with two zones.
• (b) A possible virtual geometry for this disk.

Read/write time factors:
- Seek time (the time to move the arm to the proper cylinder).
- Rotational delay (the time for the proper sector to rotate under the head).
- Actual data transfer time.

Algorithms:
- First Come-First Serve (FCFS)
- Shortest Seek Time First (SSTF)
- Elevator (SCAN)
- Circular SCAN (C-SCAN)

• Components of storage
  • Files and directories
  • Filesystems
  • Block devices, such as disks, partitions, logical volumns.
• The hard disk types
  • SATA vs SAS
• The disk inside
  • CHS and LBA
• Disk Arm Scheduling Algorithms
  • FCFS
  • SSTF
  • SCAN
  • CSCAN

• Disk partition table
• Disk partition types
• Name the disk partitions

• Hard disks can be partitioned. MBR-based Partitioning :

  • First sector: Master Boot Record
  • Maximum of four primary partitions
  • One primary partition may be an extended partition
  • An extended partition can hold an unlimited amount of logical partitions

• MBR – Master Boot Record

  • Work with BIOS
  • 32bit, max partition size: 2TB

• GPT – GUID Partition Table

  • GUID: Globally Unique Identifier
  • Support unlimited partitions
  • 64bit, max partition max size: 18EB
  • Protective MBR
  • Need OS support and mainboard support (EFI/UEFI)

• Disk partition table
  • MBR vs GPT
• Name the disk partitions
  • Primary partitions
  • Extented partitions
  • Logical partitions
• Use fdisk to display or modify the disk partition table

• Benefits of the LVM
• Component of the LVM

PROBLEMS:

• Fixed partitions
• Expanding size of the partition
• Limitation on size of a file system and a file
• Contiguous data requirement
• Time and effort required in planning ahead

• Logical volumes solve noncontiguous space problems
• Logical volumes can span disks
• Logical volume sizes can be dynamically increased
• Logical volumes can be mirrored
• Physical volumes are easily added to the system
• Logical volumes can be relocated
• Volume group and logical volume statistics can be collected

These tasks can be performed dynamically!

Logical volume management solves the disadvantages of traditional disk storage.

• One or more physical volumes (hard disks, partitions) are assigned to a volume group (VG)
• All physical volumes (PV) are split into physical extents (PE) of identical size (default 4 MB)
• Logical extents (LE) can be combined into logical volumes (LV). LE and PE share the same size. LEs are stored in PEs in a VG.
• LVs can be used like any block device
  • An LV can span multiple disks
  • To increase the size of an LV, add PEs
  • To increase the size of a VG, add PVs
• In some OS, like AIX:
  • physical extent (PE) is called physical patition (PP)
  • logical extent (LE) is called logical patition (LP)

• Physical Volumn

  • pvs, pvcreate, pvremove ...

• Volumn group

  • vgs, vgcreate, vgextend, vgreduce ...

• Logical Volumn

  • lvs, lvcreate, lvextend, lvreduce ...

• Logical Volumn Manager
  • Volumn Group
  • Physical Volumn
  • Logical Volumn
  • Physical Extention
  • Logical Extention

• Redundant Array of Independent Disks
• RAID levels

• Typical PC hard disks are:

  • Slower
  • Less reliable
  • Smaller
  • But less expensive

• RAID uses multiple hard disks in an array to create a logical device that is:

  • Faster
  • More reliable
  • Or larger
  • And still relatively inexpensive

• RAID levels 0 through 5. Backup and parity drives are shown shaded.

• Redundant Array of Independent Disks
• RAID levels
  • RAID 0
  • RAID 1
  • RAID 10 / 01
  • RAID 5

• Chapter 5: Input/Output, Modern Operating Systems . Forth Edition, Andrew S. Tanenbaum
• Unit 9: Disk Management, RAID, and LVM, Linux System Administration, ERC 7.2, IBM