Guide to Operating Systems, 4 th ed.

1. Guide to Operating Systems, 4th ed. Chapter 7: Using and Configuring Storage Devices

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 Objectives Guide to Operating Systems, 4th ed. 2

3. Disk Storage Options Today, most computers come with one or more DVD/CD-ROM drives and a fixed hard drive. These storage devices are mounted in the computer case and connect to the computer hardware through the internal cable system. 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 Guide to Operating Systems, 4th ed.

4. Disk Storage Options Guide to Operating Systems, 4th ed.

5. Hard Drive Interfaces In some older PCs, a popular hard drive interface was the Integrated Drive Electronics (IDE) interface. IDE supports connecting two devices into the IDE interface. Enhanced IDE (EIDE) – supports higher transfer speeds, connects up to four devices, and is also found in older PCs. The IDE interface was formalized in 1990 as an American National Standards Institute (ANSI) standard. ANSI refers to the IDE standard as the Advanced Technology Attachment (ATA) interface standard. Guide to Operating Systems, 4th ed.

6. Hard Drive Interfaces An ATA interface uses a parallel connection, which is a connection that sends data and control information over wires connected in parallel so that multiple data bits are sent at one time. Parallel ATA (PATA) In a PATA interface, the cable has 40 active conductors (wires), although some ATA cables actually have up to 80 wires, even though only 40 are used. The newer high-speed serial version of the ATA interface is called the Serial ATA (SATA). Uses a high-speed serial cable to achieve transfer speeds currently up to 6 Gbps. A SATA cable interface has seven conductors. Guide to Operating Systems, 4th ed.

7. Hard Drive Interfaces Besides speed, another advantage of using SATA hard drives is that the cabling takes up less space inside the computer, allowing more room for computer cards and enabling better air flow for cooling the computer through internal fans. The SATA technology led to External SATA (eSATA) An interface that enables connectivity for an external SATA drive. Through eSATA you can connect external SATA drives by plugging into an appropriate port or slot interface. Guide to Operating Systems, 4th ed.

8. Hard Drive Interfaces Current interface options include: PCMCIA and ExpressCard ports A regular Peripheral Component Internet (PCI) card slot for an eSATA drive eSATA competes with other external storage connection technologies such as USB, FireWire, and Light Peak. Light Peak – an emerging technology that is projected to be a contender for the USB peripheral device market. USB-connected hard drives use a copper wire connection. Light Peak uses an optical cable. Guide to Operating Systems, 4th ed.

9. Hard Drive Interfaces Light Peak (contid). USB 3.0 currently carries data at q top speed of 4.8 Gbps. Initial Light Peak data transfer rates can presently reach about 10 Gbps and are eventually expected to go up to 100 Gbps. Another advantage of Light Peak is that signal loss and interference on an optical cable are very small compared to copper USB cable. Small Computer System Interface (SCSI) – A relatively fast interface, that tends to be more expensive than PATA or SATA drives. Each SCSI interface can support up to 8 or 16 devices (including the controller), depending on the type of SCSI. Guide to Operating Systems, 4th ed.

10. Hard Drive Interfaces SCSI (continued) The disks or other SCSI devices are connected together in a daisy chain fashion. Each end of the SCSI cable must be electrically terminated to prevent echoes and ghost signals on the cable. Either a disk drive or an external terminator typically terminates the other end of the chain. A terminator is an electronic resistor that absorbs the electronic signal so that the signal is not reflected back onto the cable. Can be built into a device, such as a disk drive or a small apparatus that is plugged into the cable externally. Guide to Operating Systems, 4th ed.

11. Hard Drive Interfaces SCSI Configuration Guide to Operating Systems, 4th ed.

12. Hard Drive Interfaces SCSI (continued) 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 the potential of up to 12 Gbps. SAS is compatible with the SATA interface which is useful for server and storage flexibility. Guide to Operating Systems, 4th ed.

13. Hard Drive Interfaces The number of platters, heads, tracks, and sectors per track varies widely from hard disk to hard disk. Many OSs keep a table somewhere on the disk that describes the disk in great detail. This includes the Master Boot Record (MBR) and partition table which are at the beginning track and sectors of a disk. The MBR has information about partitions and how to locate them. The partition table has information about each partition on a disk: Partition type Size Location Which partition to access first to start the OS. Guide to Operating Systems, 4th ed.

14. Hard Drive Interfaces Globally Unique Identifier (GUID) Partition Table or GPT A newer way to partition disks Does not have the same limits on the number of partitions as MBR Each partition has a unique GUID in a structure that helps ensure partition identification is not subject to errors Allows OSs to handle extremely large disks. Guide to Operating Systems, 4th ed.

15. Hard Drive Interfaces 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. Guide to Operating Systems, 4th ed.

16. Hard Drive Interfaces Backup utilities Guide to Operating Systems, 4th ed.

17. Hard Drive Interfaces 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. Dynamic disks make it possible to set up ip to 2000 dynamic volumes on one disk (Microsoft recommend 32 or fewer volumes per disk. Dynamic disks also have the ability to extend volumes onto additional physical disks. Guide to Operating Systems, 4th ed.

18. Hard Drive Interfaces Dynamic (contid.) 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 Guide to Operating Systems, 4th ed.

19. Hard Drive Interfaces 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 SSD drives of over 250 GB are available, but because of expense, it is more common to see drives in configurations of 60 – 120 GB. Advantages of SSD over traditional hard drives: No moving parts No sensitive magnetic disks Faster access to data (over 50%), because there is no need to spin a drive. More reliable because there are no fragile drive platters Lower power requirements because there is no motor Guide to Operating Systems, 4th ed.

20. Hard Drive Interfaces Solid State Drives (SSD) (contid.) Disadvantage: More expensive than traditional hard disk storage SSD drives are particularly attractive for use in laptop computers because of the reduced power consumption. Guide to Operating Systems, 4th ed.

21. Hard Drive Interfaces Researchers at the University of California (Berkeley) introduced the concept of a redundant array of inexpensive (or independent) disks (RAID) to use multiple disks in a storage array. RAID arrays serve four purposes: Increased reliability Increased storage capacity Increased speed Fault tolerance RAID uses various designs, typically designated as Level 0 – Level 5 and multiple disks to reduce the chance of information being lost in the event of a hardware failure. Guide to Operating Systems, 4th ed.

22. Hard Drive Interfaces • Because RAID array implementation tends to be costly, RAID storage is used primarily on servers, with the exception of some desktop systems that are critical to a business or research function. • RAID is implemented as a combination of hardware and software. • Hardware – hard disks connected to a controller (or more than one) • Software – can be a low-level device driver that works with any RAID hardware and provides an interface to the OS to provide access to the special RAID features offered. Guide to Operating Systems, 4th ed.

23. Hard Drive Interfaces • Modern RAID systems multiple disks, offer RAID configuration capabilities at the hardware level, which to the user means that different RAID approaches can be configured at the hardware level regardless of whether the OS has features to configure RAID. Guide to Operating Systems, 4th ed.

24. CD, DVD, and Blu-Ray Compact Disc (CD) Technology A compact disc (CD) is a polycarbonate plastic disc that has a reflective optical surface that can be read by a laser. The compact disc read-only memory (CD-ROM) uses a technology in which information is pressed onto the disc one time so that it can be read or played many times. Generally used for mass distribution of software or music. Can be written to one time. Compact Disc Recordable (CD-R) A compact disc recordable create by burning the information by a laser (“burning a disc”) Similar to a CD, the data is written one time and read time after time. Guide to Operating Systems, 4th ed.

25. CD, DVD, and Blu-Ray Compact Disc Rewriteable (CD-RW) Enables you to record information from your computer. You can write to a CD-RW many times. Each time you rewrite to a CD-RW, the information on the disc has to be “blanked” (erased) prior to writing on the CD again. Guide to Operating Systems, 4th ed.

26. CD, DVD, and Blu-Ray CDs store data in a big “spiral” instead of tracks and sectors like hard disks. The spiral starts at the inside of the disc and winds itself slowly towards the outside of the disc. 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. The surface of the disc is covered with indentations (pits) that shift the position of the reflected laser light as it is returned to the pickup. 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. Guide to Operating Systems, 4th ed.

27. CD, DVD, and Blu-Ray Data on the CD can employ any or all of the following error recovery methods: Parity – A simple error detection method that typically counts the number of nonzero bits in a string of data and then sets a parity bit to reflect whether the number of nonzero bits total to an even or an odd number. If the total is an even number, it sets the parity bit (equal to 1). If the total is odd, it does not set the parity bit (equals 0). Error correction code (ECC) – Can replace errors by adding duplicate data or parity data so that missing data can be recovered. Error concealment – Uses surrounding data to help calculate approximate data to fill in for the missing data. Guide to Operating Systems, 4th ed.

28. CD, DVD, and Blu-Ray Data on the CD can employ any or all of the following error recovery methods (contid.): Cyclic redundancy check code (CRCC) – Uses an algebraic polynomial and error key to detect and overcome errors. Reed-Solomon R-S codes – An error detection and correction technique developed by Irving Reed and Gustave Solomon that uses a complex polynomial technique for addressing data errors. All five of these error recovery methods are also used on DVDs. Although the CD is a relatively delicate medium, its built-in error detection and correction make it one of the most reliable. Guide to Operating Systems, 4th ed.

29. CD, DVD, and Blu-Ray A standard CD (CD-ROM, CD-R, CD-RW) holds 737 MB of user data, but counting space for error detection information the true storage capacity is about 847 MB. The actual storage capacity on a CD depends on the recording minutes for that CD, which can be from 21 minutes (184.6 MB) to 99 minutes (870.1 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. CDs are single-sided discs. Guide to Operating Systems, 4th ed.

30. CD, DVD, and Blu-Ray The rotational speeds of CD-ROM drives range from the normal speed of an audio CD (200-500 revolutions per minute) to as high as 72 times that speed (72X). High-speed CD-ROM drives can attain data transfer rates of 88.5 Mbps. Guide to Operating Systems, 4th ed.

31. CD, DVD, and Blu-Ray • Digital video disc (DVD) – works a lot like a CD. • It is also optical medium, and it has the data written in the form of a spiral of blocks. • All data is read from the disc with the use of a laser and an optical pickup. • The 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. • On a CD, when laser light hits the layer, it is reflected. • On a DVD, the same thing happens, but, in addition to the first layer, which is a spiral that moves from the middle of the disc to the outside, the DVD has a second layer. Guide to Operating Systems, 4th ed.

32. CD, DVD, and Blu-Ray • DVDs can store information on two sides with up to two layers per side. • The second layer is read by using light that hits the disk at a different angle. • The second layer is also a spiral that is written from the outside of the disc to the inside. • DVDs come in two diameters: • 8 cm (mini DVD) • 12 cm (standard size DVD) • Each side of a 12 cm DVD can contain up to two layers and each layer can hold 4.7 GB of data. • 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 Guide to Operating Systems, 4th ed.

33. CD, DVD, and Blu-Ray Recordable and Rewritable DVDs Digital video disc-recordable (DVD-R) Digital video disc+recordable (DVD+R) Guide to Operating Systems, 4th ed.

34. CD, DVD, and Blu-Ray DVD drives and media Guide to Operating Systems, 4th ed.

35. CD, DVD, and Blu-Ray • 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 Guide to Operating Systems, 4th ed.

36. CD, DVD, and Blu-Ray Blu-Ray Drives Blu-ray discs are different from DVD/CD-ROM because the data is recorded on top of the polycarbonate layer but just under the hard coating that protects the disc from damage. 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 Blu-Ray disc is a maximum of 50 GB. This technology has the potential to reach 500 GB with the use of ultraviolet layers. Connected to computers using a SATA interface Guide to Operating Systems, 4th ed.

37. CD, DVD, and Blu-Ray Blu-Ray Drives To play a Blu-ray video on a computer, you must have a video display system (graphics card and monitor) compatible with High-bandwidth Definition (Digital) Content Protection (HDCP). A digital copy protection method that helps ensure digital content cannot be pirated. Guide to Operating Systems, 4th ed.

38. 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. Directly connects servers and storage systems without sending data over the larger or corporate network. Accomplished by tying the servers and storage systems together via a switched , full-duplex (data goes in both directions at the same time) Fibre Channel connection. Guide to Operating Systems, 4th ed.

39. Network Storage and Cloud Storage Storage Area Networks (SAN) Typical speed for most Fibre Channel’s is 8 Gbps (16 and 40 Gbps under development). Guide to Operating Systems, 4th ed.

40. Network Storage and Cloud Storage Storage area network (SAN) Guide to Operating Systems, 4th ed.

41. Network Storage and Cloud Storage InfiniBand – Challenging the Fibre Channel architecture. 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 for connecting external disk arrays of storage in SANs. Uses high speed (fabric switching) for fast data transmission of up to 300 Gbps. Guide to Operating Systems, 4th ed.

42. Network Storage and Cloud Storage 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 Guide to Operating Systems, 4th ed.

43. Network Storage and Cloud Storage 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 Guide to Operating Systems, 4th ed.

44. Network Storage and Cloud Storage Network attached storage (NAS) Guide to Operating Systems, 4th ed.

45. Network Storage and Cloud Storage • 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 the user can access and manipulate data on a remote computer accessed via the Internet or a web-based application. • User’s data is available from any location where the Internet or private network is available. • Provides fault tolerance. • If a hard drive fails, the data is still available from another hard drive or RAID array. • Examples: YouTube hosts millions of video files, Google Docs stores document files and spreadsheets. • Files can be made public or kept private. Guide to Operating Systems, 4th ed.

46. 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 A removable hard disk is a traditional hard disk with platters, heads, and a motor, and the data is magnetically recorded on platters. Guide to Operating Systems, 4th ed.

47. Removable Disks Another removable disk option: SSD Connects to the computer through a USB port When a USB 3.0 port is available (10 times the speed of USB 2.0) this removable disk technology offers the fastest data transport. This solution can be advantageous in situations where time is critical or in which the removable drive is subject to harsh conditions. Other options: eSATA and Light Peak (mentioned earlier in this chapter) Guide to Operating Systems, 4th ed.

48. USB Flash Drives Flash drives or thumb drives – plug into a USB port and have no internal moving parts. Data can be written, deleted, and modified. 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 Guide to Operating Systems, 4th ed.

49. USB Flash Drives Storage media capacities and life spans Guide to Operating Systems, 4th ed.

50. Tapes and Tape Drives • Tape backup systems are a traditional choice for backing up large amounts of data. • Tapes use magnetic storage and record data in sequential order. • Disadvantage – to find a file near the end of the tape, the 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 Guide to Operating Systems, 4th ed.