Storage

Secondary Storage Devices

• Block Device

• File Containers

Block Device

• physical device such as a hard drive

• needs to be partitioned and formatted before it can store data

  • hard drived

File Containers

• logical device

• formatted partition

Data Sizes

• Drive = Book (largest)

• Partition = Story

• Cluster = Page

• Sector = Paragraph (smallest)

Partition

• collection of consecutive sectors

Journal File System

• logs intended changes to a journal before they are made

Windows Disk Types

• Basic disks: contain basic volume such as logical drives, primary partitions

• Dynamic disks: contain dynamic volume using 5 types

Simple Dynamic Disk

• single disk

Spanned Dynamic Disk

• sequentially across multiple disks

Striped Dynamic Disk

• interleaved through multiple disks

• RAID 0

Mirrored Dynamic Disk

• one disks that is duplicated on a second disk

• RAID 1

RAID-5

• three or more disks

• uses one for parity one for fault tolerance

Windows Partitioning Strategies

• System Partitioning: contains OS files needed for booting

• Swap Partition: used to house the swap file

• Data Partition: optional, can be used to separate data

SSDs

• solid state disks

• storage device uses flash memory to store data

• Advantages:

  • fast seek times

  • no moving parts

  • silent

• Disadvantage

  • expensive

  • limited capacities

Interconnection Types

• Local

  • 1:1 - serial

  • 1:M - parallel

• SAN

  • M:M - fabric

Local Area Block Device Interconnects

• ATA

• SATA

• SCSI

ATA

• AT Attachment

• uses 40-pin ribbon cable to connect hard drives

• includes IDEm EIDE, Ultra-ATA standards

SATA

• serial ATA

• provides more bandwidth, higher speed, smaller footprint then ATA

SCSI

• small computer system interface

• usually used in high performance systems and RAID arrays

Disk Controller

• controls r/w between drives

• all transactions originate to the controller

RAID

• redundant array of inexpensive disks

• used to create a single logical disk from multiple physical disks

RAID 0

• striping

• data is distributed across multiple disks

• no redundancy

RAID 1

• mirroring

• data is duplicated across multiple disks

• no increased performance

• fault tolerance

RAID 5

• striped with parity

• data is striped across multiple disks

• parity data is kept for each set of strips

• provides some redundancy

RAID 10 or 1+0

• mirrored stripes

• stipes data across multiple disks, whicha re then mirrored

• increased performance

• fault tolerance

NAS

• network attached storage

• file storage available over the network

• connected to LAN/WAN

• already partitioned and formatted

• doesnt require dedicated hardware

• common technologies

  • SMB/CIFS

  • NFS

SAN

• storage area networks

• block level storage accessible over a network

• uses dedicated hardware to interconnect the storage

• connected to servers

SAN vs NAS

• SAN is designed for datacenter-class applications

• NAS is used for more file server applications

iSCSI

• internet small computer systems interface

• SCSI command protocol over TCP/IP

• transfer data over IP

iSCSI Initiator

• device that originates a session to a storage device

• iQN most common apprach

iSCSI Target

• the storage device the initiator connects to

LUN

• logic unit number

• logical drive/partition presented over the network

• each target contains multiple LUNs

iSCSI Naming

• iSCSI qualified names

• IDNs

iSCSI Enumeration

• name resolution

• network storage devices must be enumerated before hey can be accessed