تهيه كننده : علي برادران هاشمي گارگاه کامپیوتر Secondary Storage

2 The primary disk used for mass storage is the hard disk drive. Hard disks differ by technology, interface, speed, and capacity. Most are capable of at least 5,000 revolutions per minute (RPM). Hard Disk Drives

3 The first PC hard disks a capacity of 10 megabytes $100 per MB Modern hard disks 100 gigabytes Less than 1 cent per MB! improvement of 1,000,000% in just under 20 years, or around 67% cumulative improvement per year. Hard Disk Drives

4 HDD Evolution

5 Hard Disk Trends Areal Density now exceeding 35 Gbits/in 2 20 GB of data onto a single 3.5" platter!

6 Capacity 100GB Spindle Speed 7200 RPM (IDE/ATA drives) 15,000 RPM SCSI drive Form Factor 5.25" drives have disappeared 3.5" drives dominating the desktop and server segment. In the mobile world, 2.5" drives. Hard Disk Trends (Cont.)

7 Performance Both positioning and transfer performancepositioning and transfer performance seek time and latency will be the areas of greatest value to hard disk engineers. seek timelatency Reliability it's much harder to improve the reliability of a product when it is changing rapidly. Interfaces IDE/ATA and SCSI. IDE/ATASCSI Hard Disk Trends (Cont.)

8 platters It consists of a series of platters spindle Platters are connected to a spindle, which in turn is connected to an electric motor. The more platters, the larger the capacity Both sides of each platter has it ’ s own read/write head The read/write heads move back and forth across the platters using a head actuator. Hard Disk Components

9 Bits on disk - dark stripes are 0 bits and bright stripes are 1 bits

10 Head crash event that happens when the surface of the read/write head or particles on its surface come into contact with the surface of the hard-disk platter, causing the loss of some or all of the data on the disk

11 tracks Information is recorded in a circular fashion in what are called tracks. cylinder A cylinder is a vertical stack of tracks on multiple platters.. sectors Tracks are divided into sectors. cluster A cluster is the smallest unit that DOS uses to store information (also called an Allocation Unit). Drive Geometry

12 Constant Angular Velocity (CAV)

13 A single data block

14 Seek, Latency, Transfer time

15 The time a program or device takes to locate a single piece of information and make it available to the computer for processing. Disk access times are measured in milliseconds (thousandths of a second), often abbreviated as ms. Fast hard disk drives for personal computers boast access times of about 9 to 15 milliseconds. Note that this is about 200 times slower than average DRAM. The access time for disk drives includes the time it actually takes for the read/write head to locate a sector on the disk (called the seek time). This is an average time since it depends on how far away the head is from the desired data. Average Access Time

16 The speed with which data can be transmitted from one device to another. Data rates are often measured in megabits (million bits) or megabytes (million bytes) per second. These are usually abbreviated as Mbps and MBps, respectively. In reference to the disk drive, it is the speed at which it can transfer information from the drive to the processor. Data Transfer Rate

17 A process that involves writing data to every other sector as the disk rotates, instead of sequentially to every sector. The disk drive can access only one sector at a time, and the disk is constantly spinning beneath the read/write head. This means that by the time the drive is ready to access the next sector, the disk may have already spun beyond it. If a data file spans more than one sector and if the sectors are arranged sequentially, the drive will need to wait a full rotation to access the next chunk of the file. If instead the sectors are staggered, the disk will be perfectly positioned to access sequential sectors. Stated in ratios (I.e., 1:1, 2:1, 3:1) Sector Interleaves

18 In one-to-one interleaving, the sectors are placed sequentially around each track. In two-to-one interleaving, sectors are staggered so that consecutively numbered sectors are separated by an intervening sector. Interleaving

19 Removable hard drives Hot swap Disk Arrays RAID (redundant array of inexpensive disk) Mirrored array (fault-tolerant) Striped array Alternative technologies

20 Information supplied with the hard drive will give you: the number of cylinders gives you the number of tracks per side the number of heads gives you the number of sides the number of sectors what do you think! Capacity

21 IDE Intelligent Drive Electronics Abbreviation of either Intelligent Drive Electronics or Integrated Drive Electronics, depending on who you ask. IDE was the term first used to refer to drives using the ATA standard. It is an interface for mass storage devices, in which the controller is integrated into the disk or CD-ROM drive. Today however, all drives have integrated logic boards, even those that do not use this interface. The "proper" name for the IDE interface is AT Attachment, or ATA. Hard Disk Interfaces

22 AT Attachment AT Attachment a disk drive implementation that integrates the controller on the disk drive itself. ATA and IDE are the same thing, with an interface that is 16 bits wide to match the old AT bus. master slave The specification calls for a single channel, shared by two devices that are configured as master and slave. ATA includes support for PIO modes 0, 1 and 2 ATA includes support for single word DMA modes 0, 1 and 2, and multiword DMA mode 0. ATA

23 The only practical difference is that the PC will assign drive letters to the master drive before the slave drive, so that if you have a master and slave on the primary IDE channel and each has only one regular, primary partition, the master will be "C:" and the slave "D:". This means that the master drive (on the primary channel) is the one that is booted, and not the slave. Master/Slave Designation

24 A newer version of the IDE mass storage device interface standard developed by Western Digital Corporation. It supports data rates of between 4 and 16.6 MBps, about three to four times faster than the old IDE standard. It can support mass storage devices of up to 8.4 gigabytes, whereas the old standard was limited to 528 MB. Because of its lower cost, enhanced EIDE has replaced SCSI in many areas. EIDE is sometimes referred to as Fast ATA or Fast IDE, which is essentially the same standard, developed and promoted by Seagate Technologies. It is also sometimes called ATA-2. Enhanced IDE (EIDE)

25 ATA-2: Supports faster PIO modes (3 and 4) and multiword DMA modes (1 and 2). Also supports logical block addressing (LBA) and block transfers. ATA-2 is marketed as Fast ATA and Enhanced IDE (EIDE). PIO Mode MB/s PIO Mode MB/s DMA Multiword MB/s DMA Multiword MB/s ATA-2

26 The newest version of the AT Attachment (ATA) standard, which supports burst mode data transfer rates of 33.3 MBps. To take advantage of these high speeds, your computer must also be equipped with Ultra DMA, a protocol that supports faster data transfer rates to and from hard disk drives. UDMA is a more advanced technology which provides for even faster throughput, up to 33.3 MB/s in UDMA mode 2 and 66.7 MB/s in UDMA mode 4, twice to four times that of EIDE, for much lower prices than SCSI. Many new computers come with large UDMA drives and UDMA interfaces, and it's possible to add a UDMA interface card (such as the Promise Ultra33 or Ultra66) to an existing system to boost speed, even on older non-UDMA drives. Ultra ATA

27 Logical Block Addressing Logical Block Addressing A method used with SCSI and IDE disk drives to translate the cylinder, head, and sector specifications of the drive into addresses that can be used by an enhanced BIOS. LBA is used with drive's that are larger than 528 MB, and require an enhance BIOS that can handle LBA. Logical Block Addressing (LBA) is used to allow DOS and Windows to use drives over 504MB. Logical Block Addressing (LBA) is used to allow DOS and Windows to use drives over 504MB. LBA Addressing

28 Small Computer Systems Interface Small Computer Systems Interface, a standard developed by the American National Standards Institute (ANSI). It specifies a universal, parallel, system-level interface for connecting up to eight devices (including the controller) on a single shared cable (called a SCSI bus). A SCSI device can install on any SCSI bus, whether on a Mac, PC, or any computer with a SCSI adapter. SCSI

29 SCSI-1: Uses an 8-bit bus, and supports data rates of 4 MBps SCSI-2: Same as SCSI-1, but uses a 50-pin connector instead of a 25-pin connector, and supports multiple devices. This is what most people mean when they refer to plain SCSI. Wide SCSI: Uses a wider cable (168 cable lines to 68 pins) to support 16-bit transfers. Fast SCSI: Uses an 8-bit bus, but doubles the clock rate to support data rates of 10 MBps. Fast Wide SCSI: Uses a 16-bit bus and supports data rates of 20 MBps. Ultra SCSI: Uses an 8-bit bus, and supports data rates of 20 MBps. Current varieties of SCSI

30 SCSI-3: Uses a 16-bit bus and supports data rates of 40 MBps. Also called Ultra Wide SCSI. Ultra2 SCSI: Uses an 8-bit bus and supports data rates of 40 MBps. Wide Ultra2 SCSI: Uses a 16-bit bus and supports data rates of 80 MBps. Ultra320 SCSI : maximum throughput of 320MB/s using 80 MHz bus signaling Current varieties of SCSI(Cont.)

31 Remember that the SCSI specification allows devices other than a hard drive to be connected to the same cable, both internally and externally The host adapter and every device must have a SCSI ID number between 0 and 7. Usually, the host adapter is factory set at 7, the highest priority ID. The cable must be terminated at both ends (the host adapter probably is self-terminating, and is commonly placed at one end. Make sure the termination is enabled. If the adapter is in the middle, you will need terminators at both ends.) What ’ s important about SCSI

32 1. Low level formatting (LLF) This is the "true" formatting process for the disk. It creates the physical structures (tracks, sectors, control information) on the hard disk. Normally, this step begins with the hard disk platters "clean", containing no information. 2. Partitioning This process divides the disk into logical "pieces" that become different hard disk volumes (drive letters). This is an operating system function. 3. High level formatting (HLF) This final step is also an operating-system-level command. It defines the logical structures on the partition and places at the start of the disk any necessary operating system files. Disk Formating

33 Redundant Arrays of Inexpensive Disks use of multiple hard disk drives in an array that behaves in most respects like a single large increased capacity, performance and reliability but they come with real costs.Nothing in life is free. RAID

34 Same magnetic medium as the hard disk, but uses a thin floppy disk encased in a protective casing. The drive geometry is the same as the hard disk, with the exception of not having a cylinder (in this case, a cylinder would be the same as a single track. It is rare to find anything other than the 3.5” 1.44 MB diskette drive in current systems. Floppy Drives

35 An IDE system supports two devices, both of which are attached to the same data cable. An EIDE system supports four devices. This is due to the use of two controllers, both of which provide for up to two devices on each cable. Note that each EIDE controller supports two devices, and that is why the total is four. Know how many devices an IDE/EIDE system can support:

36 Master/slave designations must be used in an IDE system with multiple drives. The master drive is the drive whose controller will manage the multiple drives. They are configured using a jumper. Know the significance of the master/slave designations and how to change them:

37 There are actually 2 sizes using 5 capacities that you could run into: Size Tracks/sdSectors/trk Capacity 5.25” DD KB 5.25” HD MB 3.5” DD KB 3.5” HD MB 3.5” ED MB Floppy Drive Capacities

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39 Reel to reel and cartridge Magnetic Tape

40 CD-ROM High density storage Read-only storage removable DVD-ROM Better than CD-ROM 7 times density comparing to CD-ROM WORM disks Write once read many Magneto-Optical Disks Using both magnetic and optical techniques Optical and Magneto-Optical disk storage

41 A removable disk on which data is written and read through the use of laser beams Optical disk

42 Constant linear velocity (CLV) for maximum capacity

43 Self-Monitoring Analysis and Reporting Technology SMART

44 Any Question?