Storage Technology Flashcards (Lec 10)

Flashcards for reviewing Storage Technology lecture notes.

Block Device

Physical storage device such as a hard drive.

File Container

Logical storage device such as a formatted partition.

Formatting

The process of creating a file system on a block device.

Block Devices

Examples include magnetic hard disks, solid state drives, and optical drives.

Optical Drives

Examples include CD, DVD, and Blu-Ray.

RAID arrays

Can be implemented in hardware or software for storage.

Storage Area Networks

Includes Fibre Channel, iSCSI, and AON.

Sector

The smallest unit of storage on a hard disk.

File system

The management of sectors is a function of this.

SSDs

Becoming more available as the technology gets better.

RAM technology in SSDs

Requires constant power for data persistence in some SSDs.

NAND-based flash memory

Retain memory without power and are slower than RAM-based SSDs.

Solid State Drives

Fast seek times and no moving parts are advantages of this.

Solid State Drives

Expensive, wear leveling, and limited capacities are disadvantages of this.

Hybrid Drives

Combines a large HDD with a smaller SSD cache.

Block devices

Consist of the media and read/write mechanism and the interconnect/attachment.

Controllers

Hardware connected to the computer that connects to block devices.

Interconnection Types

Local 1:1, serial, 1:M, parallel, Storage Area Network M:M.

ATA (AT Attachment)

Uses a 40-pin ribbon cable.

SATA (Serial ATA)

Provides more bandwidth, higher speed, and smaller footprint than ATA.

SCSI (Small Computer System Interface)

Usually used in high performance systems and RAID arrays.

Drive Physical storage mechanism

Platters, heads, etc.

Disk Controller

Controls read/write from/to drives.

RAID

Can be used to aggregate multiple drives into a single, fault-tolerant, higher-performing, storage device

RAID

Used to create a single logical disk from multiple physical disks.

Hardware RAID

Operations are managed by the attachment controller.

Software RAID

Done by the operating system.

RAID 0 (Striping)

Data is distributed across multiple disks for increased performance but no redundancy.

RAID 1 (Mirroring)

Data is duplicated across multiple disks for fault tolerance.

RAID 5 (Striped with parity)

Data is striped across multiple disks with parity data for redundancy.

RAID 10 or 1+0 (Mirrored Stripes)

Stripes data across multiple disks, which are then mirrored for increased performance and fault tolerance.

A block device

Represents a series of blocks and clusters that store data directly.

File systems

Used to hold variable length files.

Record/Page/Block systems

Used to hold fixed length data.

Partitions

Each physical disk is broken into one or more of these.

Volumes and Slices

Physical block devices are divided or aggregated into these.

Physical Disk

Contains volumes, which contain partitions, which are formatted to create file systems.

Basic disks

Contain basic volumes.

Dynamic disks

Contain dynamic volumes.

Simple Volume

Uses free space from a single disk.

Spanned Volume

Uses free space sequentially across multiple disks.

Striped Volume

Uses free space that is interleaved through multiple disks (i.e., RAID 0).

Mirrored Volume

Uses free space on one disk that is duplicated on a second disk (i.e., RAID 1).

RAID-5 Volume

Uses free space across three or more disks and uses one for parity for fault tolerance.

Primary Partitions

The default method of creating space in a volume (basic or dynamic).

Extended Partitions

Can be created in place of a primary partition.

Logical Drives

Can be created within an extended partition.

System Partition

Contains OS files and files needed for booting.

Swap Partition

Can be used to house the swap file.

Data Partition

Optional, can be used to separate data from other programs and files.

Master Boot Record (MBR)

In Intel x86 systems, the system boots from this.

MBR

Stored in the boot sector, an area just before the first partition.

MBR

Tells the system where to find the active, bootable partition.

Extended Boot Records (EBR)

Non-active primary partitions and extended partition information is stored here.

Windows Master Boot Record

Tells the system where to find the active, bootable partition.

MBR

Transfers control to NTLDR (NT Loader) which executes and figures out where OS files are.

File Systems Purpose

To store and organize files.

Journal

A journaling FS logs intended changes to this before they are made.

File System Journaling

Reduces the likelihood of corruption and adds to the stability of the FS.

LFN

Long File Names support up to 255 UTF-16 compatible characters.

NTFS

Use this for hard drives.

FAT32

Use this for removable media.

Storage Area Networks (SAN)

Block level storage accessible over a network.

Network Attached Storage (NAS)

File level storage that is available over the network.

SAN

Designed for datacenter-class applications.

NAS

Used for more file server applications.

iSCSI

Standardized in 2003 by IETF RFC 3720-2723.

iSCSI

SCSI command protocol over TCP/IP.

iSCSI

Uses TCP Port 3260.

Initiator

Device that originates a session to a storage device.

Target

The storage device to which an initiator connects.

LUN (Logic Unit Number)

A Logical drive/partition presented over the network.

Network fabric

The interconnection between nodes, typically Ethernet.

Initiators

Devices that push/pull data from network storage.

Targets

Network storage devices that contain LUNs.

iQN

Most commonly used approach for iSCSI naming.

IQN

Supported by internet Storage Name Service (iSNS).

EUI

Based on IEEE unique identifier like MAC addresses.

SendTargets

An iSCSI target server is queried by the initiator for the list of available targets.

Logon

An initiator associates with a target.

Authentication

Provided by CHAP.

One way CHAP

Target authenticates initiator

Mutual CHAP

Target and initiator authenticate each other

iSCSI Authorization

Based on initiator node name or IP address.

Block Devices Examples

Includes Magnetic hard disk, Solid State Drives, Flash, SSD, Optical Drives, CD, DVD, Blu-Ray, RAID arrays Hardware Software Storage Area Networks Fibre Channel, iSCSI, AON

Block Device File Container

Partition created, formatted for NTFS

Magnetic Hard Disk

A sector can contain only one file. If a file takes up .5 of a sector, the other half is wasted Sector management is a function of the file system

Solid State Drives

Require constant power for data persistence Some have batteries or external power to maintain data in case of power loss Since 2009 most use NAND-based flash memory Retain Memory without power Slower than RAM based SSDs

Solid State Drives Advantages

Fast seek times No moving parts Silent operation

Solid State Drives Disadvantages

Expensive Wear leveling Limited capacities Power requirements Little improvement to sustained read/write performance

Hybrid Drives available

Combine Large HDD with smaller SSD cache Improve performance of frequently accessed files Not all advantages of SSDs are realized For files not in the SSD cache, drive performs as a HDD would

Controllers

Hardware connected to the computer Via a motherboard chip or expansion card Connect to block devices

ATA (AT Attachment)

Uses a 40-pin ribbon cable to connect hard drives, CD drives, etc. Includes the IDE, EIDE, Ultra-ATA standards

SATA (Serial ATA)

Provides more bandwidth, higher speed, and smaller footprint then ATA

SCSI (Small Computer System Interface)

Usually used in high performance systems and RAID arrays Parallel and Serial implementations available

Storage Layers and Hierarchy

All transactions are originated by the controller RAID Can be used to aggregate multiple drives into a single, fault tolerant, higher performing, storage device Viewed as a single block device by higher layers Either single drives or RAID can be used as basic block storage

RAID Redundant Array of Inexpensive Disks

Used to create a single logical disk from multiple physical disks Can be used to realize Increased Performance Fault tolerance Both Can be implemented in hardware or software

Hardware RAID

The RAID looks like a single large drive to the computer RAID operations are done in hardware Hardware XOR engine Does not use processor clock cycles or memory Creates a single point of failure If the RAID controller fails, the entire array is down

Software RAID

Can limit what RAID types are available for the operating system itself Uses processor clock cycles and memory Physical drives are partitioned into special RAID partitions That are then combined into a single logical block device

RAID 0 (Striping)

Data is distributed across multiple disks Increased performance No redundancy If one disk fails, all data is lost