Hard Drive Technologies Joe Cicero Northeast Wisconsin Technical College
This Presentation Will Cover… • Types of Hard Drives • SATA, ATA, SCSI, etc • Hard Drive Parts • Platter/s, Read/Write Head/s, Actuator Arm/s, Actuator, Spindle, etc. • How A Hard Drive Works • Modifying Magnetic Media • Hard Drive Math • Why 1000 = 1024
Continued… • Hard Drive Controllers • IDE, EIDE, SCSI, SATA, RAID, etc • Configuring Hard Drives • Jumpers, Master, Slave, Cable Select, IDE / EIDE Cable capabilities, etc. • Partitioning A Hard Drive • Primary, Extended, Logical Drives • Format of Hard Drive • FAT, NTFS, EXT3, etc
Continued… • Hard Drive Maintenance • Chkdsk, cleanmgr, defrag, limitations, etc.
Types of Hard Drives • Hard drives come in many different types. Some of these are: • ATA • ATA : Also known as IDE (Integrated Drive Electronics) supports one or two hard drives per cable, a 16-bit interface and PIO (Programmed Input/Output).
Types of Hard Drives Continued: • SATA • SATA or S-ATA, an evolution of the ATA physical storage interface. Serial ATA is a serial link -- a single cable with a minimum of four wires creates a point-to-point connection between devices. Transfer rates for Serial ATA begin at 150 MBps and SATA II 300MBps. • One of the main design advantages of Serial ATA is that the thinner serial cables facilitate more efficient airflow inside a form factor and also allow for smaller chassis designs.
Types of Hard Drives Continued: • SCSI • This acronym is pronounced "scuzzy" and stands for Small Computer Systems Interface. IDE and SATA are much more common and less expensive. • The biggest difference between SCSI, ATA and SATA is that while SCSI has a processor integrated into the controller, ATA and SATA make greater use of the system processor to serve that function. • SCSI is more expensive and also more flexible and generally the drive spins faster – but it should be noted that spinning faster doesn’t necessarily make it work faster with the OS. • With a single SCSI card you can have 15 or more devices whereas typically you are only allowed to have 4 devices with an ATA/IDE or SATA system.
Hard Drive Parts A - Platter/s B - Read/Write Head/s C - Actuator Arm/s D - Actuator E - Spindle
How A Hard Drive Works • The banks of polarized molecules in the disk's coating are themselves tiny magnets that create a magnetic field through which the read/write head passes. The movement of the head through the magnetic field generates an electrical current that travels in one direction or the other through the wires leading from the head. The direction the current flows depends on the polarities pf the bands. By sensing the directions in which the current is moving, the computer can tell if the read / write head is passing over a 1 or a 0.
Hard Drive Math • kilo is 1,000 in the decimal system. • Hence, one kilometer is a 1,000 meters and one kilogram is 1,000 grams because we are using the decimal system. • However, in the binary system, a kilo is 1,024. • As you can see the kilo in the binary system (1,024) is close in value to the kilo in the decimal system (1,000) and many people use 1 kilobyte as a synonym of 1,000 bytes. • Therefore, a file of 6 KB contains 6,144 bytes (6 x 1024 bytes) not 6000 bytes. A 2.2 Gig hard drive partition would have 2,252,800,000 bytes or would be 2.2528 GB.
Hard Drive Controllers • IDE • Integrated Device Electronics. A hard drive interface system developed by a group of manufacturers whereby the controller system was integrated into the drive; all of the components were within the hard drive unit removing the need to have a separate controller. • It should be NOTED that most older 40 wire IDE cables DO NOT support Cable Select! • EIDE • A design that improves on the Drive limitations of the IDE design. EIDE designs can use up to four devices (split into two pairs). For each pair of devices, one of the devices is the master; the drive electronics on the master control both the master drive and (if applicable) the secondary slave unit attached. • It should be NOTED that the Master Drive should be plugged into the end of the cable if you want it to be a master device and are setting it to Cable Select!
Hard Drive Controllers • SCSI • Small Computer Systems Interface, a high-speed communications protocol that allows computers, samplers, and disk drives to communicate with one another. Pronounced "scuzzy.“ • It should be noted that when using SCSI interfaces you can have up to 7 (or even 15) devices. • SATA • Serial ATA is an evolutionary replacement for the Parallel ATA physical storage interface.
Hard Drive Controllers • RAID (Redundant Array of Independent Disks). A collection of disk drives that offers increased performance and fault tolerance. There are a number of different RAID levels. The three most commonly used are 0, 1, and 5: • * Level 0: striping without parity (spreading out blocks of each file across multiple disks). • * Level 1: disk mirroring or duplexing. • * Level 2: bit-level striping with parity • * Level 3: byte-level striping with dedicated parity. Same as Level 0, but also reserves one dedicated disk for error correction data. It provides good performance and some level of fault tolerance. • * Level 4: block-level striping with dedicated parity • * Level 5: block-level striping with distributed parity • * Level 6: block-level striping with two sets of distributed parity for extra fault tolerance • * Level 7: Asynchronous, cached striping with dedicated parity
Configuring Hard Drives • Most IDE drives have jumpers that select the "master" or "slave" role on the controller, but modern drives also have a "CS" or "Cable select" pin. This allows the IDE cable itself to select the drive's role: all drives that have the CS jumper set allow the cable to choose which device is the master and which is the slave.
Configuring Hard Drives • When a drive is on the cable alone it should be set to Master OR Cable Select – providing it is plugged into the end connector. • When there are two drives, the drive that should be bootable should be set to Master or Cable Select – providing it is plugged into the end connector.
Configuring Hard Drives • When there are two drives, one that is bootable, one that is not; The bootable drive should be set to Master or Cable Select – providing it is plugged into the end connector. • When there are two drive, both that are bootable; They should be both set to Cable Select.
Configuring Hard Drives • SATA does not require Master Slave settings. SATA drops the master/slave shared bus of PATA, giving each device a dedicated cable and dedicated bandwidth. While this requires twice the number of host controllers to support the same number of SATA devices
Partitioning A Hard Disk • Primary Partitions:A primary partition may contain an operating system along with any number of data files (for example, program files, user files, and so forth). Before an OS is installed, the primary partition must be logically formatted with a file system compatible to the OS. • If you have multiple primary partitions on your hard disk, only one primary partition may be bootable and active at a time. The active partition is the partition from which an OS is booted at computer startup. • Primary partitions other than the active partition are hidden if their file system type is not recognized, preventing their data from being accessed. Thus, the data in a primary partition can be accessed (for all practical purposes) only by the OS installed on that partition. • If you plan to install more than one operating system on your hard disk, you probably need to create multiple primary partitions; most operating systems can be booted only from a primary partition.
Partitioning A Hard Disk • Extended Partitions:The extended partition was invented as a way of getting around the arbitrary four-partition limit. An extended partition is essentially a container in which you can further physically divide your disk space by creating an unlimited number of logical partitions. • An extended partition does not directly hold data. You must create logical partitions within the extended partition in order to store data. Once created, logical partitions must be logically formatted, but each can use a different file system.
Partitioning A Hard Disk • Logical Partitions • Logical partitions may exist only within an extended partition and are meant to contain only data files and operating systems that can be booted from a logical partition (for example, Linux, Windows NT, and so forth).
Formatting A Hard Disk • Formatting a hard disk arranges the magnetic media in a pattern so that the operating system knows where it is in relation to the data on the disks surface • When doing a clean install of Windows XP, after you’ve selected the partition where XP will be installed, you are presented with the option to format the drive or partition. The format options are: • Format the partition using the NTFS file system (Quick) • Format the partition using the FAT file system (Quick) • Format the partition using the NTFS file system • Leave the current file system intact (no changes) • The difference between the regular format versus the quick format is whether or not the volume is scanned for bad sectors using the chkdsk command. Both methods remove the files from the volume.
Format Choices • FAT16 • The FAT16 file system was introduced way back with MS–DOS in 1981. It was designed originally to handle files on a floppy drive, and has had minor modifications over the years so it can handle hard disks, and even file names longer than the original limitation of 8.3 characters, but it's still the lowest common denominator. • The biggest advantage of FAT16 is that it is compatible across a wide variety of operating systems, including Windows 95/98/Me, OS/2, Linux, and some versions of UNIX. By default many of these OS’s can read FAT16! • The biggest problem of FAT16 is that it has a fixed maximum number of clusters per partition, so as hard disks get bigger and bigger, the size of each cluster has to get larger. In a 2–GB partition, each cluster is 32 kilobytes, meaning that even the smallest file on the partition will take up 32 KB of space. FAT16 also doesn't support compression, encryption, or advanced security using access control lists.
Format Choices • FAT32 • The FAT32 file system, originally introduced in Windows 95 Service Pack 2, is really just an extension of the original FAT16 file system that provides for a much larger number of clusters per partition. As such, it greatly improves the overall disk utilization when compared to a FAT16 file system. • However, FAT32 shares all of the other limitations of FAT16, and adds an important additional limitation—many operating systems that can recognize FAT16 will not work with FAT32—most notably Windows NT, but also Linux and UNIX as well. • Now this isn't a problem if you're running FAT32 on a Windows XP computer and sharing your drive out to other computers on your network—they don't need to know (and generally don't really care) what your underlying file system is.
Format Choices • NTFS • The NTFS file system, introduced with first version of Windows NT, is a completely different file system from FAT. It provides for greatly increased security, file–by–file compression, quotas, and even encryption. It is the default file system for new installations of Windows XP. • There are DOS and Legacy Windows drivers to allow older systems to read NTFS. Unix/Linux also has a NTFS driver, so these OS’s can read NTFS partitions.
Hard Drive Maintenance • Chkdsk • If your Windows operating system experiences a problem, you can use the Chkdsk disk repair utility included in the operating system to check the file system on each logical partition and check the disk surface for unreadable or corrupted sectors. • The Chkdsk utility creates and displays a status report for a disk based on the file system used. Chkdsk also lists and corrects errors on the disk. You can run Chkdsk from your Windows operating system. If you cannot start your operating system because of the problem, you can run Chkdsk from the Windows Recovery Console.
Hard Drive Maintenance • CleanMGR • Cleanmgr.exe is designed to clear unnecessary files from your computer's hard disk. You can configure Cleanmgr.exe with command-line switches to clean up the files you want. You can then schedule the task to run at a specific time by using the Scheduled Tasks tool. • It is important to clean your disk of unnecessary files BEFORE you defrag it!
Hard Drive Maintenance • Sometimes when you install a program or create a data file, the file ends up chopped up into chunks and stored in multiple locations on the disk. This is called fragmentation. • There's a simple solution to file fragmentation: use Windows Disk Defragmenter (Start –> Programs –> Accessories –> System Tools –> Disk Defragmenter). This utility, commonly called Defrag, gathers all the scattered file fragments and writes them into adjacent clusters, so each file occupies a contiguous section of the disk. • Defrag works by moving slabs of data to unused parts of the disk, in order to open up a large free section of space. It then assembles the fragmented parts of a file and writes them in one complete piece to the cleared space; it then does the same with the next file; and so on until the entire disk is defragmented.
Hard Drive Maintenance • Defrag Limitations • Defrag cannot defragment open files or Operating System Files that are in use. • To over come this limitation you can use specialty software programs. • Pagedfrg – is a utility to defragment the pagefiles • Contig – is a utility to defragment individual files.