2.Storage Devices

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Introduction to Stora e

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Devices


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Outline

What is Storage Device

Types Of Storage Devices

Disk based Devices

Access based devices

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Flash Drives

Array Devices

Tape Devices Storage Lab Visit


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Storage Devices

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What is storage device

Device which holds data or program Device capable of storing data

It is a hardware device which is designed to store theinformation

Example: Hard disk, CD, Floppy or memory chips such as

memory sticks, Compact flash memory etc

Usuall this term is used while referrin to mass stora e

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devices such as Disk Drives or tape drives

Classification of Storage Devices: Storage devices can be

classified (one of the way) based on- Availability of information

- Type of data storage or accessing method

- Connectivity


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Types of Storage Devices

Based on Availability of information

Volatile (RAM): Device which loses the information when electricallynot powered on. Also referred as RAM or main memory. Example: Mainmemory

Non-volatile devices (NVM or NVRAM or EPPROM) : Device whichdoes not loose information when powered off. Data is permanentlystored or is ersistent on the device. Exam le Hard disk Flo CD

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Memory sticks etc

Based on data Storing/Accessing type

Sequential: Device where data can be read/written in a sequential

manner. Example: Tape Device Random Access: Device where the data can be accessed at any

order, i.e. at random. Example: Main memory


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Types of Storage Devices

Classification based on device connectivity:

1. Primary Storage: Main memory directly accessible to the CPU.

2. Secondary Storage: Not directly accessible by the CPU. Thecomputer usually uses its input/output channels to access secondarystorage and transfers desired data using intermediate area in primarystorage. Example: Hard Disk

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.dismount removable mass storage media into a storage deviceaccording to the system's demands. It is primarily used for archival ofrarely accessed information. Example: Tape Library

4. Off-line Storage: a computer data storage on a medium or a device

that is not under the control of a processing unit . The medium isrecorded, usually in a secondary or tertiary storage device, and thenphysically removed or disconnected. Example: Optical discs, flashmemory, external hard disk drives, magnetic tape


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Type of Devices - Disk Based

Hard DiskNon-volatile Random Access

device used to store data.

Hard disks use multiple platters,stacked on a spindle. Each

Platter has two read/write heads,

one for each side.

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Interface: IDE, USB, SCSI, FC,SAS

Capacity: 20- 3TBGB

Data Transfer Rate: Over100MB/s

Manufacturer: Seagate,

IBM, Maxtor, Western

Digital


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Type of Devices - Disk Based

IDE/ATA/Parallel-ATA Disk:Advanced Technology Attachment

(ATA) is a standard interface for

connecting storage devices such

as hard disks and CD-ROM drives

inside personal computers.

Serial ATA (SATA) Disk: Advantages

- Thinner cables that let air cooling work

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more e c ent y

- Faster transfers

- Support for hot swapping

External USB Hard Disk (Advantages)

- Can connect externally to the computer- Portable

- Can store much larger quantities of datathan USB pens, CD-R or even writeableDVDs


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Type of Devices Access Based

NVRAM: Stands for Non-Volatile RAM (Random Access Memory). NVRAM ismanufactured with a built in battery which keeps power applied to the memory afterpower has been removed from the product. The primary advantage of an NVRAM isspeed.

Flash Memory: is non-volatile computer memory that can be electrically erased and

reprogrammed. It is a technology that is primarily used in memory cards, and USBflash drives (thumb drives, handy drive, memory stick, flash stick, jump drive) forgeneral storage and transfer of data between computers and other digital product

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Reference: http://en.wikipedia.org/wiki/NVRAM

http://en.wikipedia.org/wiki/Flash_memory


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Type of Devices Flash drives

Flash drive : A flash drive, is a storage device that uses flash memory rather thanconventional spinning platters to store data. Unlike a USB flash drive, flash drives

tend to physically imitate conventional hard drives in size, shape, and interface sothat they may act as a replacement for hard drives.USB flash drive: USB flash drives are NAND-type flash memory data storage

devices integrated with a USB (universal serial bus) interface. They are typicallysmall, lightweight, removable and rewritable and are more reliabledue to their lack of moving parts. USB flash drives offer potential advantages over

other portable storage devices (floppy disk).

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Reference: http://en.wikipedia.org/wiki/Flash_disk

http://en.wikipedia.org/wiki/USB_flash_drive


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Array Devices JBOD

JBOD (just a bunch of disks) refers to hard disks that can be combined toAct as a single larger volume. It doesnt has any storage controllerintelligence or data redundancy capabilities

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JBOD can combine hard disks of different sizes into a single unit withoutloss of any capacity. If a drive in a JBOD set dies then it may be easier torecover the files on the other drives


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Array Devices RAID

RAID combines physical hard disks into a single logical unit andreplicate data among multiple hard drives for increased reliability andperformance either by using special hardware or software. Hardwaresolutions often are designed to present themselves to the attached

system as a single hard drive, and the operating system is unaware ofthe technical workings. Advantages are Higher Data Security, FaultTolerance, Improved availability, Increased & Integrated Capacity andImproved Performance

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Three key concepts in RAID are Mirroring- the copying of data to morethan one disk, striping-the splitting of data across more than one diskerror correction-the storage of redundant data is to detect andpossibly fix the problem (known as fault tolerance). Different RAIDlevels use one or more of these techniques, depending on the systemrequirements.


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RAID controllers and Arrays

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RAID Arrays

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RAID Device Single RAID Levels

Level 0: Provides data striping(spreading out blocks of eachfile across multiple disks) but no redundancy. This improvesperformance but does not deliver fault tolerance.

Level 1: Provides disk mirroring.

Level 2: Bit-level striping with Hamming code ECC.

Level 3: Same as Level 0, but also reserves one dedicateddisk for error correction data. It provides good performance

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v u .

Level 4: Block-level striping with dedicated parity.

Level 5: Provides data striping at the byte level and alsostripe error correction information. This results in excellent

performance and good fault tolerance. Level 6: Block-level striping with dualdistributed parity.

Level 7: Asynchronous, cached striping with dedicatedparity.


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Tape DevicesLINUX Servers with Qlogic

/ Emulex HBAsSunFire V240

with Qlogic HBAsWindows server withQlogic / Emulex HBAs

McData / CNT switch

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IBM FastT200

FC-SANBrocade SAN Switch (3200) Brocade SAN Switch (3800)

Tape Library StorageTek /

IBM/Adic

LSI ProFibre JBOD

Serial ATA

Tape Drive StorageTek /

HP/IBM


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Basic Storage DevicesA tape drive is a data storage device that reads and writes data storedon a Magnetic tape It is typically used for archival storage of data storedon hard drives . Tape media generally has a favorable unit cost and longarchival stability.

Tape Drives

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Interfaces: SCSI, FC etcCartridge Capacity: 20 - 200 GB

Native Data Transfer Rate: 10 35 MB/s

Archival Life: 15 30 yearsManufacturers: IBM, HP, SONY, QUANTUM

Tape Drives

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drives only allow for sequential-access of data. As a result, tape

drives have very slow average seek times.

Despite the slow seek time, tapes drives can stream data totape very quickly. For example, modern LTO drives can reachcontinuous data transfer rates of up to 80 MB/s, which is as fastas most 10,000 rpm hard disks


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Composite Storage Devices Tape LibraryTape library (sometimes called a tape silo or tape jukebox) is a storagedevice which contains one or more tape drives, a number of slots to holdtape cartridges, a barcode reader to identify tape cartridges and anautomated robot for loading tapes.

Capacity: Up to 90PBNumber of cartridge slots: Up to 30 - 30,000Number of drives: 2 - 2,048

Tape Library

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, , , .

Libraries provide large storage capacity at a very cheap rate. They haveslow access time( varies from seconds to minutes), which usually involvesmechanical manipulation of tapes..

Tape libraries are primarily used for backups and as the final stage ofdigital archiving


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Composite Storage Devices Tape Library

Tape Library

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Documents

2.Storage Devices