Storage Systems and Technologies, Study notes of Information and Communications Technology (ICT)

Download Storage Systems and Technologies and more Study notes Information and Communications Technology (ICT) in PDF only on Docsity! Storage 1 2 Learning Objectives 1. Name several general properties of storage systems. 2. Describe the two most common types of hard drives and what they are used for today. 3. Discuss the various types of optical discs available and how they differ from each other. 4. Identify some flash-memory-based storage devices and media and explain how they are used today. 5. List at least three other types of storage systems. 6. Summarize the storage alternatives for a typical personal computer. 5 Logical vs. Physical Representation • File: Anything stored on a storage medium, such as a program, document, digital image, or song • Filename: Name given to a file by the user • Folder: Named place on a storage medium into which files can be stored 6 Storage Technologies • Magnetic (conventional hard drives) • Optical (optical discs) • Electronic (flash memory media) 7 Hard Drives  Hard drive: Used to store most programs and data  Can be internal and external  Magnetic hard drives  Use metal hard disks  Read/write heads magnetize particles to represent the data’s 0s and 1s  Solid-state drives (SSDs)  Use flash memory technology  Use less power and have no moving parts  Particularly appropriate for portable computers Solid State Drives (SSDs) Data is stored in flash memory ——— chips located inside the drive; there are no moving parts like in magnetic hard drives. FIGURE 3-6 Solid-state drives (SSDs). External Hard Drives FIGURE 3-7 : External hard drives. — 5 FULL-SIZED EXTERNAL HARD DRIVES PORTABLE HARD DRIVES (MAGNETIC) JAre about the size of a 5 by 7-inch picture Are about the size of a 3 by 5-inch index card_ but frame, but thicker; this dive holds 1.5 TB. thicker; this drive holds 500 GB. PORTABLE HARD DRIVES (SSD) EXPRESSCARD HARD DRIVES Are about the size of a credit card, Fit into an ExpressCard slot; this but thicker: this drive holds 18 MB. drive holds 32 GB. 12 Hard Drive Speed … DAT  Disk access time (DAT): Total time that it takes for a hard drive to read or write data. Consists of  Seek time: the time required for read/write head to move to the cylinder that contains (or will store) the desired data.  Rotational delay: the time required for the mounting shaft to rotate the disks into the proper position.  Data movement time: the time required for the system to read the data from the disk and transfer it to the RAM or to transfer the data to be written to the disk from RAM and then store it on the disk.  DAT = Seek time + rotational delay + Data movement time  Typically value: 10 to 20ms  Minimizing seek time can improve DAT. 15 Partitioning and File Systems  Partitioning: Logically divides the physical capacity of a single drive into separate areas, called partitions  Partitions function as independent hard drives  Referred to as logical drives  Older OS allowed HDD up to 512MB, HDD larger than that used to have multiple partitions.  Partitioning a large drive make it more efficient, because OS typically use larger cluster size with a larger drive.  When a large cluster size is used, disk space is often wasted because even tiny files have to use up one entire cluster.  When a drive is partitioned, each logical drive uses a smaller cluster size since drive is smaller.  FAT 32 file system more efficient than FAT 16 Partitioning and File Systems • Partitions used to: – Create a recovery partition – Create a new logical drive for data – Create a dual boot system (i.e. windows and Linux) • File system: Determines the cluster size, maximum drive size, and maximum file size – FAT, FAT32, and NTFS Partitioning and File Systems rie PW Oren E> ae Rerricaetie Oi oF age Parrecoyubta D8 ote (0) FIGURE 3-9 Hard drive partitions. New personal computers today often come with the primary hard drive divided into two partitions. 20 Storage Systems for Large Computer Systems and Networks • Storage server: Hardware device containing multiple (array of) high-speed hard drives • Businesses have to store tremendous amounts of data – Business data – Employee and customer data 21 RAID  RAID (redundant arrays of independent discs): Method of storing data on two or more hard drives that work together to do the job of a larger drive  Usually involves recording redundant copies of stored data  Helps to increase fault tolerance  Different levels (0 to 5) of RAID:  RAID 0 = disk striping (spread files over two or more hard drives)  RAID 1 = disk mirroring (duplicate copy)  Other levels use a combination of striping and mirroring with error correction provisions. RAID STRIPING When a tile is written to a RAID system using striping, it is split among two or more drives. FIGURE 3-23 RAID. Two primary RAID techniques are striping and mirroring MIRRORING When a file is written to a RAID system using mirroring, an identical copy of the file is sent to another drive in the system. Flash Memory Systems Flash memory card EMBEDDED FLASH MEMORY FLASH MEMORY CARDS AND READERS USB FLASH DRIVES Flash memory is often embedded into Flash memory cards are often used to store data for digital USB flash drives are often used to store data consumer products, such as this digital cameras and other devices; the data can be transferred to and tranefer files from one computer to media player, for storage purposes. a computer via a flash memory card reader, as needed. another. , FIGURE 3-15 Flash memory systems. Flash memory is used in a variety of storage systams today. Flash Memory Cards FIGURE 3-16 Flash memory cards. Show GL MEMORY STICKS (COMPACTFLASH (CF) CARDS OLYMPUS << FLASH MEMORY CARD READERS. SECURE DIGITAL (SD) CARDS. XD PICTURE CARDS Can be built-in or extemal and usually support several different types of flash memory media; extemal readers such as this one typically connect to a computer via a USB port. 27 USB Flash Drives • USB flash drives: Consist of flash memory media and a reader in a single self-contained unit – Typically portable drives that connect to and are powered by a USB port – Also called USB flash memory drives, thumb drives, jump drives 30 Smart Cards  Smart card: Credit card-sized piece of plastic that contains some computer circuitry (processor, memory, and storage)  Stores small amount of data (about 64 KB or less)  Commonly used to store prepaid amounts of digital cash or personal information  Smart card readers are built into or attached to a computer, keyboard, vending machine, or other device  Some smart cards store biometric data  Can be used in conjunction with encryption and other security technologies Smart Cards USING A SMART CARD TO LOG ON TO A COMPUTER USING A SMART CARD TO ACCESS A SECURE FACILITY James Anderson Security Manager HOOF LS 28, ‘Smart cand circuitry ASMART CARD USING A SMART CARD TO PAY FOR A VENDING MACHINE PURCHASE ) FIGURE 3-20 Smart cards. Smart card 32 Optical Discs • Optical discs: store data optically (using laser beams) • Divided into sectors like magnetic discs but use a single spiral track (groove) • Data is stored in 0s and 1s • Pits and lands are used to represent 1s and 0s, the transition between a pit and a land represents a 1; no transition represents a 0 • Can be: • Read-only • Recordable or rewritable 35 Read-Only Discs  Read-only disc: Can be read from, but not written to, by the user  CD-ROM (compact disc read-only memory)  DVD-ROM (digital versatile disc read-only memory)  BD-ROM (Blu-Ray disc read-only memory)  Normally come pre-recorded  Software programs  Clip art and other graphics  Music  Movies  Games (UMD, Wii, Xbox, etc.) 36 Recordable Discs • Recordable disc: Can be written to, but cannot be erased and reused • CD-R discs • DVD-R/DVD+R discs; can be dual-layer • BD-R; can be dual-layer • Used for back up, sending large files to others, creating custom music CDs, storing home movies, etc. 37 Rewritable Discs • Rewritable disc: Can be recorded on, erased, and overwritten just like magnetic discs – CD-RW – DVD-RW – BD-RE; can be dual layer