9781111306366 ppt ch7

Guide to Operating Systems, 4th ed.

Chapter 7: Using and Configuring Storage Devices

Guide to Operating Systems, 4th ed. 2

Objectives

2

• Explain common disk storage technologies

• Back up data using operating system tools

• Explain network storage technologies

• Discuss removable disk storage

• Describe tape drive technologies

• Explain storage management tools in different operating systems


Disk Storage Options

• Today, most computers come with one or more DVD/CD-ROM drives and a fixed hard drive

• Removable hard drives and flash drives can be connected through USB ports and other communication channels

• “Disk” refers to a hard drive and “disc” refers to an optical medium, such as a CD or DVD

Disk Storage Options



Hard Drive Interfaces

• In some older PCs, a popular hard drive interface was the Integrated Drive Electronics (IDE) interface

• Enhanced IDE (EIDE) – supports higher transfer speeds, connects up to four devices, and is found in older PCs– American National Standards Institute (ANSI) – refers to the

IDE standard as the Advanced Technology Attachment (ATA)

• The newer high-speed serial version of the ATA interface is called Serial ATA (SATA)

• External SATA (eSATA) – interface that enables connectivity for an external SATA drive



• Through eSATA you can connect external SATA drives by plugging into a port or slot interface– Interface options include PCMCIA and Express Card

• Light Peak – an emerging technology that is projected to be a contender for the USB peripheral device market (uses an optical connection)

• Small Computer System Interface (SCSI) – relatively fast interface that can support up to 8 or 16 devices – Disks and other SCSI devices are connected together in a

daisy chain fashion



• SCSI (continued)– Each end of the SCSI cable must be electrically terminated to

prevent echoes and ghost signals on the cable– A terminator is an electronic resistor that absorbs the signal

• Can be built into a device, such as a disk drive

– Advances in SCSI have resulted in several enhancements: Ultra SCSI, Ultra wide SCSI, Ultra2 SCSI, Ultra2 wide SCSI, Ultra3 SCSI (Ultra 160), Ultra320 SCSI, and Ultra640 SCSI

• Ultra640 transfers at a rate of 640 MBps, has a 16-bit bus, handles 16 devices and used for servers and network storage

– Serial Attached SCSI (SAS) – new technology that supports up to 16,256 devices, has initial speeds in the 3-6 Gbps range, and is compatible with the SATA interface



SCSI Configuration



• Globally Unique Identifier (GUID) Partition Table or GPT – a new way to partition disks– Allows OSs to handle extremely large disks

• Windows System Information utility is a way to view the hard drive configuration on your computer

• Hard disk failures do happen so backing up your computer is an essential practice

• Most OSs today offer Backup utilities that make backing up data easier– Examples of those utilities are listed in the table on the next

slide



Backup utilities



• Basic and Dynamic Disks – Windows OS has the ability to distinguish between these two disk types– Basic – a physical hard drive that contains primary and

extended partitions, or logical drives that are known as volumes

– Dynamic – volumes that can span multiple disks• Fault tolerance is supported – involves implementing software or

hardware to protect against hardware failures, power interruptions, and lost data

• Supported by all editions of Windows Server 2003/R2 and Windows Server 2008/R2

• Supported by some later versions of Windows desktop versions

• Basic disks can be converted to dynamic disks by using the Disk Management tool in Windows



• Solid State Drives (SSD) – a storage technology that uses semiconductors for storage– Similar technology is used in flash drives but SSDs are larger

than flash drives and hold more data

• Advantages of SSD over traditional hard drives:– No moving parts– No sensitive magnetic disks– Faster access to data – More reliable because there are no fragile drive platters– Lower power requirements because there is no motor

• Disadvantage:– More expensive than traditional hard disk storage



• RAID Arrays – Redundant array of inexpensive (or independent) disks

• RAID arrays serve four purposes:– Increased reliability– Increased storage capacity– Increased speed– Fault tolerance

• Various RAID designs, typically designated as Level 0 – Level 5

• RAID can be costly and is primarily used on servers


• RAID is implemented as a combination of hardware and software– Hardware – hard disks connected to a controller (or more than

one)– Software – provides an interface to the OS to provide access to

special RAID features offered

• Modern RAID systems offer configuration at the hardware level (does not need OS to configure RAID)

• RAID is covered in more detail in Chapter 11



CD, DVD, and Blu-Ray

• Compact Disc (CD) Technology – a polycarbonate plastic disc that has a reflective optical surface that can be read by a laser

• CD-ROM – compact disc read-only memory uses a technology in which information is pressed onto the disc one time (read or played many times)

• CD-R – compact disc recordable – information can be burned onto the disc by a laser one time– Commonly called “burning a disc”

• CD-RW – compact disc rewriteable – you can write to the disc many times



• CDs store data in a big “spiral” instead of tracks and sectors like hard disks

• When a disc is read:– Laser light is emitted by the CD-ROM drive head and reflected

off the disc surface onto an optical pickup– Surface is covered with indentations or “pits”, depending on the

size of the pits, ones or zeros are returned– The surface of the CD reflects light during a data read

operation

• CDs are very sensitive to scratches and other kinds of damages that can hinder optical readout



• Data on the CD can employ any or all of the following error recovery methods:– Parity – simple error detection method that typically counts the

number of nonzero bits in a string of data, then sets a parity bit to reflect whether the bits total to an even or odd number

– Error correction code (ECC) – can replace errors by adding duplicate data or parity data so missing data can be recovered

– Error concealment – uses surrounding data to help calculate approximate data to fill in for the missing data

– Cyclic redundancy check code (CRCC) – uses an algebraic polynomial and error key to detect and overcome errors

– Reed-Solomon R-S codes – uses a complex polynomial technique for addressing data errors



• A standard CD holds 737 MB of user data, but counting space for error detection the true storage capacity is about 847 MB

• CDs are rated in terms of recording minutes as well as megabytes of data because they are used for music or audio as well as for data

• Rotational speeds of CD-ROM drives range from the normal speed of 200-500 revolutions per minute to as high as 72 times that speed (72X)


• Digital video disc (DVD) – works a lot like a CD but storage capacity and data transfer rate of a DVD are much higher than for a CD

• DVDs can store information on two sides with up to two layers per side– Unlike CDs, DVDs have a second layer that is read by using

light that hits the disk at a different angle

• A single-layer single-sided DVD holds 4.7 GB of data– A double-layer single-sided DVD holds 8.54 GB and a double-

layer double-sided DVD holds up to 17.08 GB of data




• Recordable and Rewritable DVDs– Digital video disc-recordable (DVD-R)– Digital video disc+recordable (DVD+R)



DVD drives and media


• DVD/CD-ROM Drives– Usually connected to a computer using a hard disk

interface

– Most PCs use the SATA, EIDE, or SCSI interface

– Require different drivers than hard disk drives

– Most PCs have drivers built into the BIOS system and boot system

• This enables computers to boot an OS from a CD or DVD

– Most PCs can boot an OS directly from a CD or DVD for initial installation




• Blu-Ray Drives– Blu-ray discs are different from DVD/CD-ROM because the

data is recorded on top of the polycarbonate layer• Enables the information on the disc to be read more accurately

without the problem of “disc tilt”

– Data transfer speed can reach 36 MBps (compared to about 10 MBps for DVDs)

– Current storage capacity of a disc is a maximum of 50 GB– Connected to computers using a SATA interface– To play a Blu-ray video on a computer, you must have a video

display compatible with High-bandwidth Definition Content Protection (HDCP)


Network Storage and Cloud Storage

• Organizations today are dealing with massive amounts of data – Backups, disaster recovery, and availability of data are reasons

why storage area networks and cloud storage are growing in popularity

• Storage Area Networks (SAN) – a grouping of storage devices that form a small private network– Data transfer between servers and storage systems takes

place on Fibre Channel– Typical speed for most Fibre Channel’s is 8 Gbps (16 and 40

Gbps under development)



Storage area network (SAN)



• InfiniBand – designed for ultrafast connectivity in data centers, such as linking servers for clustering to act as one powerful server– Emerged as an alternative to Fibre Channel

• Network attached storage (NAS) – a way to directly attach storage to a local area network (LAN)– Works with multiple OSs– Allows most clients to access the storage on the network using

TCP/IP (standard network communications protocol)– Different than a SAN – servers communicate with the storage

over the main network rather than by a separate Fibre Channel



• NAS can use Internet Small Computer System Interface (iSCSI) for communications– Offers TCP/IP-based communication that enables connectivity

with SCSI-based storage arrays – Faster data access than Fibre Channel because data

transmission speeds are linked to the actual speed of the network

– Because it uses TCP/IP, can be used on LANs, WANs, or over the Internet

– Disadvantage: creates extra network traffic which can lead to network congestion



Network attached storage (NAS)


• Cloud Storage – available through the Internet or through Web-based applications– Data may be transferred over the Internet or network to the

user’s computer or user can manipulate data on a remote computer via the Internet

– User’s data is available from any location where Internet is available

– Provides fault tolerance – Examples: YouTube hosts millions of video files, Google Docs

stores document files and spreadsheets – Files can be made public or kept private



Removable Disks

• Early examples were floppy disks and Zip disks– Storage capacities from 1.44 MB – 750 MB

• Today, users expect removable storage capacities to match hard disk capacities– Some removable hard disks that connect to USB ports can

hold over 1 TB of data

• Another removable disk option: SSD– Connects to the computer through a USB port

• Other options:– eSATA and Light Peak (mentioned earlier in this chapter)


USB Flash Drives

• Flash drives or thumb drives – plug into a USB port and have no internal moving parts– Don’t require additional drivers and are quickly recognized by

PnP– Easy to use and fit in your pocket– Typical sizes (at this writing) include 4, 8, 16, 32, and 64 GB– Work with Windows, UNIX/Linux, and Mac OS X

USB Flash Drives

Storage media capacities and life spans


Tapes and Tape Drives

• Tape backup systems are a traditional choice for backing up large amounts of data

• Use magnetic storage and record data in sequential order– Disadvantage – to find a file near the end of the tape, drive

must first go through all of the data recorded prior to that file– Access to data is typically slower than a removable hard drive

• Most popular for long-term storage– With disk drives growing into terabytes, tape drive technology

is continuing to evolve in order to keep up



Tape media capacities



• DAT Drives - Digital audio tape– Use a 4-mm tape and the digital data storage (DDS) format– DDS-1 has a capacity of 2 GB (4 GB compressed)– Current standard is DDS-5 – storage capacity of 36 GB (72 GB

compressed)– Backward compatible – can upgrade to a DDS-5 drive and still

read DDS-4 tapes– Rated at an archival life of 10 years– Still used for audio recordings, but use for data storage is

mostly replaced by other tape technologies



• DLT Drives – Digital linear tape– Use half-inch wide magnetic tapes– Record data in tracks – Offers a high-speed search capability – a file can be found in a few

seconds to a little over a minute– Used in many automated tape backup systems

• SDLT Drives – Super digital linear tape– Use both magnetic and optical recording methods– Laser technology can more accurately write data to the tape and

allows for greater density of information• Up to 2.4 TB compressed

• Both DLT and SDLT have an archival life of up to 30 years



• AIT Drives – Advanced intelligent tape (AIT)– First introduced in 1996 and used mainly in midrange servers– Tapes have an erasable memory chip inside the cartridge that

stores information normally written at the beginning of the tape• Can fast forward and pinpoint information faster

– Started out with a capacity of 35/90 GB

• S-AIT Drives – Super advanced intelligent tape– Has a capacity of 500 GB/1.3 TB (native/compressed)

• Both of these drives can sustain up to 30,000 tape passes and have an archival life of 30 years



• LTO Drives – Linear tape open– Most widely accepted in high-end servers (because of high-

speed performance)– Standards are open to the public and are nonproprietary– LTO Ultrium format was developed so that LTO tapes can be

used in existing DLT tape drives• For faster conversion to LTO Ultrium technology

– Offer fast data transfer speed of up to 240 MBps, for noncompressed data and 120 MBps for compressed data

– Can sustain up to 260 tape passes and have an archival life of 15-30 years


Storage Management Tools

• Windows Storage Management Tools– Windows Disk Management tool for hard drive and removable

storage is available in the following versions:• Windows XP/Vista/7, Server 2003/R2, and Server 2008/R2

– Enables you to:• Create, format, and delete partitions

• Manage partitions

• Manage removable storage such as hard drives, DVD/CD-ROM drives, and flash drives

• Convert a basic disk to a dynamic disk

– Can access this tool from Computer Manager– Other utilities are Disk Defragmenter, chkdsk, and format



Windows Disk Management tool in Windows 7



• Disk Management Tools in UNIX/Linux– Common command-line utilitities: fdisk, format, sfdisk, and

cfdisk– sfdisk and cfdisk enable you to verify partitions, list information

about partitions, and repartition a disk– Command-line utility mount – mounts a file system so that you

can use a disk partition• Many need to manually mount file systems for DVD/CD-ROM or

flash drives

– In Linux with the GNOME desktop, there are GUI tools to manage disk storage




GNOME Disk Utility


Summary of UNIX/Linux disk management commands



• Mac OS X Disk Utility – available to partition, format, and manage hard drives, DVD/CD-ROM drives, removable hard drives, flash drives, and other storage– Options available depend on the type of storage medium

selected• When you select a storage medium in the left pane, the utility

displays appropriate tabs for the actions you can perform on that storage medium

• Because Mac OS X is UNIX-based, you can also open a terminal window and use the mount command to manage storage media



Mac OS X Snow Leopard Disk Utility


Chapter Summary

• This chapter provides an introduction to how OSs interface with storage devices and gives an overview of storage device technologies

• Popular computer storage technologies include hard disk drives, solid state drives, RAID arrays, CD, DVD, and Blue-Ray technologies that interface to the computer through the OS and device drivers

• An important part of learning to manage hard disk storage is performing backups

• Network storage devices include storage area networks (SANs) and network attached storage (NAS)

• Cloud storage enables users to access storage through the Internet or a network using Web-based interfaces


Chapter Summary

• SANs can use Fibre Channel or InfinitBand technology and NAS can use iSCSI storage technology

• Modern medium- to large-capacity removable storage includes USB attached removable hard drives, USB solid state drives, eSATA drives, Light Peak drives, and USB flash drives

• Common tape storage options include DAT, DLT, SDLT, AIT, S-AIT, and LTO tapes and drives

• Operating systems come with storage management tools, such as the Windows Disk Management tool, the Disk Utility in GNOME for Linux, and the Mac OS X Disk Utility


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