Chapter 5 Final

Storage TypeDescription

Hard disk drive
(HDD)

A hard disk is a thick magnetic disk encased in a thicker protective shell. Key facts are:

• A hard disk consists of several aluminum platters, each of which requires a read/write head for each side.

• All read/write heads are attached to a single access arm to prevent them from moving independently.

• Each platter has circular tracks that cut through all the platters in the drive to form cylinders.

• The spinning of the platters is referred to as revolutions per minute (RPM). The higher the revolutions per minute, the faster the data can be accessed.

Standard hard drives are categorized as follow:

• 5400 rpm (inexpensive HDD)

• 7200 rpm (good quality HDD)

• 10,000 rpm (expensive HDD)

• 15,000 rpm (fast HDD)

Some advantages of hard disks are:

• They have large amounts of storage (starting at 16 GB up to several TB).

• The cost per MB is cheap.

• There is a wide selection.

Some disadvantages of hard disks are:

• Many hard disks are internal devices, though you can get external enclosures.

• They are prone to failure.

• They are vulnerable to physical damage (e.g., when dropped).

SCSI is a standard for transferring data between devices on internal and external computer buses. Though SCSI devices are most commonly used for tape storage devices and hard disks, they can also be used for devices such as CD-ROM drives, scanners, and printers.

Solid state drive
(SSD)

A solid-state drive is a flash device with a storage capacity similar to a small hard drive. Solid state drives are used as replacements for hard disk drives for storing the operating system, applications, and data files.

Some advantages of solid-state drives include:

• They are faster than hard drives.

• They have no moving parts.

• They have lower power consumption than hard drives (good for laptops).

• They are less susceptible to physical damage (from dropping) and immune from magnetic fields.

• They are smaller and lighter than hard drives.

The main disadvantage currently for solid state drives is cost. They are often more expensive than comparable hard drives. However, their advantages make them a good choice, especially for portable devices.

Non-Volatile Memory Express
(NVMe)

NVMe is a memory storage device designed to allow access to non-volatile storage media through a PCI express (PCIe) bus.

NVMe is designed to work well with the low latency and internal parallelism of solid-state storage devices. By allowing host hardware and software to utilize the level of parallelism possible in modern SSDs, NVMe reduces I/O overhead and improves functionality.

NVMe devices come in three forms. The most common are standard-sized PCI Express expansion cards and 2.5-inch form-factor devices that provide a four-lane PCI Express interface through the U.2 connector. There are also storage devices that use SATA Express and the M.2 specification, which support NVMe as the logical device interface.

Flash devices

Flash memory cards store information using programmable, non-volatile flash memory. Some of the advantages of flash devices are:

• The memory is re-programmable.

• They can retain content without power.

• They are optimal for use in devices, such as cameras.

• They are highly portable.

• They have a larger capacity than CDs and DVDs.

• They have relatively fast memory access.

• They are inexpensive

Additional advantages of flash devices are:

• Their storage capacity is comparable to the capacity of modern hard disks.

• Most new PCs have card readers.

• They are versatile to use.

Common flash memory cards include:

• CompactFlash cards

• SD cards

• SSD cards

• MiniSD cards

• MicroSD cards

• Hybrid cards (combines SSD and HDD technology)

• Memory sticks

Optical disc

Optical discs (such as CDs, DVDs, and Blu-ray discs) are a storage medium that uses lasers for both reading and writing information. Optical discs store information through pits in their reflective coating. As the disc spins, the optical drive sends laser optics to the disk and receives the stored information through the deflected output.

Some advantages of optical discs are:

• They are great for music and video (they play in audio or video devices that aren't computers).

• They are portable and universal.

• They are cheap.

• You can buy discs that are recordable.

• They have a long shelf life and are relatively sturdy.

• Blu-ray discs can store a large amount of data (25 GB or more, depending upon the format).

Some disadvantages of optical discs are:

• They are slower than hard disks.

• They have a small capacity (650 MB for CDs, 4.7 GB for DVDs).

• There are some compatibility issues between disc formats and readers.

Integrated Drive Electronics
(IDE)

An electronic interface allows communication between a motherboard's data paths (or bus) and a computer's hard disks.

StandardDescription

SATA1

SATA1 is the original SATA standard. It provided for 1.5 Gbps (1500 MBps) data transfer.

SATA2

The second generation of SATA devices support up to 3 Gbps (3000 MBps). SATA2 includes the following enhancements:

• Hot pluggable support, allowing drives to be added and removed while the system is running.

• Improved connectors to reduce electrostatic discharge (ESD), improved usability, and extended life when used with external devices.

• Native Command Queuing (NCQ) for increased performance.

• Port multiplier support, allowing multiple devices to be connected to a single SATA port.

SATA3

The third generation of SATA devices supports up to 6 Gbps (6000 MBps).

• This standard mainly addresses solid state drives with SATA (hard disk drives are not capable of sending data at this rate).

• SATA 3.5 is the latest revision.

• The standard includes new connectors for solid state devices and thin optical drives.

• Device transmit emphasis for Gen 3 PHY brings SATA in line with other features of I/O measurement solutions.

• Xbox One S features SATA III connections.

eSATA

The external SATA (eSATA) standards are a subset of other standards specifically for externally connected devices.

• eSATA devices use a special SATA data cable with a locking clip to prevent the cable from being accidently disconnected.

• Because power is not supplied through the SATA data cable, eSATA devices require an external power connector or power source.

• eSATA has a rectangular connector.

eSATAp

The Power over eSATA or Power eSATA (eSATAp) standard is meant to replace eSATA.

• eSATAp combines the functionality of an eSATA and a USB port for a source of power in a single connector.

• Both SATA data and device power are integrated in a single cable.

• The eSATAp connector and port are neither an L-shaped or rectangular.

RAID LevelDescription

RAID 0 (striping)

A stripe set breaks data into units and stores the units across a series of disks by reading and writing to all disks simultaneously. Striping:

• Provides an increase in performance.

• Does not provide fault tolerance. A failure of one disk in the set means all data is lost.

• Requires a minimum of two disks.

• Has no overhead because all disk space is available for storing data.

RAID 1 (mirroring)

A mirrored volume stores data to two (or more) duplicate disks simultaneously. If one disk fails, data is present on another disk. The system switches immediately from the failed disk to a functioning disk. Mirroring:

• Provides fault tolerance for a single disk failure.

• Does not increase performance.

• Requires a minimum of two disks.

• Has overhead. Overhead is 1 / n where n is the number of disks. If data is written twice, half of the disk space is used to store the second copy of the data.

• RAID 1 is the most expensive fault tolerant system.

RAID 5 (striping with distributed parity)

A RAID 5 volume combines disk striping across multiple disks with parity for data redundancy. Parity information is stored on each disk. If a single disk fails, its data can be recovered using the parity information stored on the remaining disks. Striping with distributed parity:

• Provides fault tolerance for a single disk failure.

• Provides an increase in performance for read operations. Write operations are slower with RAID 5 than with other RAID configurations because of the time required to compute and write the parity information.

• Requires a minimum of three disks.

• Has an overhead of one disk in the set for parity information (1 / n).

  • A set with 3 disks has 33% overhead.

  • A set with 4 disks has 25% overhead.

  • A set with 5 disks has 20% overhead.

RAID 10 (stripe of mirrors)

A RAID 10 volume stripes data across mirrored pairs and across multiple disks for data redundancy. If a single disk fails, its data can be recovered using the mirrored information stored on the remaining disks. If two disks in the same mirrored pair fail, all data will be lost because there is no redundancy in the striped sets.

• Provides fault tolerance for a single disk failure.

• Provides redundancy and performance.

• Uses 50% of the total raw capacity of the drives due to mirroring.

• Requires a minimum of four disks.

Features

Description

Upgrade the Hard Disk

Upgrade to the fastest hard disk possible. Hard disk drives come in a variety of different rotation speeds such as:

• 5400 RPM (not desired)

• 7200 RPM (minimum)

• 10,000 RPM

• 15,000 RPM

Upgrade the Disk Interface

Upgrading your disk interface will greatly improve the throughput of data to and from your hard disk drive. For optimal performance, consider upgrading to SATA3. This will upgrade your speed to 600 MBps.

Utility

Description

Disk Cleanup

Disk Cleanup helps manage disks by locating and disposing of files that can be safely removed from the disk by:

• Emptying the Recycle Bin

• Deleting temporary files such as those used by a web browser or for application installation

• Deleting installation log files

• Deleting offline files

• Compressing old files

You can type Cleanmgr at the command prompt to run Disk Cleanup.

Disk Defragmenter

Disk Defragmenter optimizes the performance of your hard drive by joining fragments of files that are in different locations on your hard drive into a single location.

• To improve defragmentation, disable programs that run in the background like screensavers and virus software. Any disk access while Disk Defragmenter is running (whether to read from or write to the disk) will slow down the defragmentation process.

• The more information that is on the drive, the more time it will take to defragment the drive.

Run Defrag at a command prompt to run Disk Defragmenter in a text mode.

Check Disk

Check Disk is a utility that verifies the file system integrity of a hard disk. Errors that can be checked and fixed by Check Disk include:

• Lost clusters are a series of used clusters on the hard disk drive that are not associated with a specific file.

• A cross-linked file occurs when two files claim the same cluster. Check Disk will identify cross-linked files and correct their cluster associations.

• Orphaned files are files that exist on the hard drive but are not associated with a directory in the index. Normally Check Disk can re-associate the file with the correct directory.

• A bad sector is a portion of the hard disk that cannot be used. Bad sectors are marked so that they are no longer used. Any used bad sectors are redirected to another sector.

The NTFS file system automatically detects bad sectors as the system operates saving and reading files.

You can run Check Disk by typing Chkdsk at a command prompt.

• Use Chkdsk with the /f switch to automatically fix errors without scanning for bad sectors.

• Use the /r switch to scan and fix bad sectors and other errors.

• Use the /? command for help.

Issue

Description

Defragmentation

On an SSD storage device, fragmentation is much less of an issue than it is for standard hard disk drives. File systems such as NTFS still fragment files when writing them to the drive in order to optimize storage space. However, an SSD storage device doesn't have read-write heads, and no repositioning must occur to read heavily fragmented files. As a result, fragmented files can be read as quickly as contiguous files.

When working with SSD drives, you should not defragment them as you do standard hard disk drives. This is because SSDs wear out over time. Each cell in a flash memory bank has a finite lifetime and can only be written to and erased a certain number of times before it fails. Running defragmentation utilities causes unnecessary write/erase operations to occur. Use Security and Maintenance in Control Panel to disable automatic disk defragmentation on SSD storage devices.

Mean Time Before Failure (MTBF)

Because of the way they are constructed, an SSD storage device has a lifespan called the mean time before failure, which is usually much shorter than standard hard disk drives. Each time a write/erase operation occurs, it consumes some of the finite lifetime of the flash memory chips within the SSD device.

Be aware that some applications running on the system can overuse SSD storage devices. For example, audio, graphic, and especially video editing applications commonly require a very large number of write/erase operations and can cause SSD storage devices to fail prematurely. However, these applications also benefit greatly from the increased speed offered by SSD storage devices. Therefore, if you chose to use SSDs with these types of applications, you should consider configuring an automatic data backup process (such as Windows Backup and Restore or File History) to protect the data stored on the SSD drive on a traditional hard disk drive.

Some system builders implement a mix of storage devices in high performance systems so that:

• Heavily used information is stored on a standard hard disk drive. For example, the Windows operating system and its applications may be installed on a less expensive but more durable standard hard disk drive.

• Only data that requires high performance is stored on SSD storage devices.

• Important data on the SSD is automatically backed up on the standard hard disk drive.

TRIM

One method for extending an SSD device's life is to enable TRIM functionality. TRIM configures the operating system to communicate with an SSD device and to tell it which blocks of data on the device are no longer required and can be wiped clean. This prevents the SSD device from storing unnecessary data and being overused.

Later versions of Windows should automatically detect the presence of an SSD device and enable TRIM. You can verify this by opening a command window and entering fsutil behavior query DisableDeleteNotify.

This command will return either a 0 or a 1. A value of 0 indicates that TRIM is enabled, but a value of 1 indicates that it is not. If it is disabled, you can manually enable TRIM on an SSD drive by entering fsutil behavior set DisableDeleteNotify 0.

Issue

Device Type

Resolution

Slow Performance

HDD

Several things can help increase the performance of a slow HDD:

• Maintain a healthy amount of free disk space on the drive. A mostly empty disk runs faster than a mostly full disk. If a disk is getting full, migrate to a newer, bigger disk.

• Keep the disk defragmented. A heavily fragmented disk can run quite slowly. You'll need ample free space to fully defragment the drive.

• Check the disk rotational speed. A disk that spins faster will perform better.

• Check the speed of the disk interface. If your system uses an older disk interface, upgrade to a faster interface (if possible).

SSD

The more an SSD is used, the slower the read/write speed will be.

• Make sure the file system being used is optimized for an SSD. Because SSDs store data differently than HDDs, they require special techniques to extend the life of the drive, such as wear leveling support.

• Update the SSD's firmware. Newer firmware versions are released to fix bugs and optimize how the SSD stores data.

• Run a manufacturer-specific SSD software utility. Most SSD manufacturers have specialized utilities that can check for errors and optimize an SSD's performance.

• Check the speed of the SATA connection. Older SATA versions have slower transfer speeds than newer SATA versions. If performance is too slow, consider upgrading components to the latest SATA version.

• When the SSD is too full, performance will decrease significantly. If this happens, try enabling features such as TRIM support in the OS.

While features such as TRIM will help to an extent, the best way to maintain high performance is keeping an SSD below 90% capacity.

Failure to Boot (OS not Found)

HDD/ SSD

A failure to boot with an error message that reads something to the effect of "OS Not Found" could be trivial or serious. Common causes include the following:

• You're booting from the wrong disk ; one that doesn't have an operating system installed. This is a very common issue. It frequently occurs when a CD or DVD is in your optical drive at system boot and the BIOS/UEFI is configured to boot from the optical drive first. The error message is displayed when an operating system can't be found on the optical disc. To fix this issue, simply remove the optical disc from the drive and reboot.

• This error could also be caused in situations where you have multiple hard disks in the system, but only one has an operating system installed. If the boot device setting gets inadvertently changed in the BIOS/UEFI, it will try to boot the system from the wrong hard disk.

• Your master boot record (MBR) has been overwritten or is corrupt. The MBR is the first sector of your hard drive that tells the BIOS where to look for the operating system on the disk. If the MBR is damaged or corrupt, then the operating system will fail to load.

  On Windows, you have to boot from the installation disc to enter the recovery environment and select the Automatic repair option. Alternatively, you can select the Command prompt option and run the bootrec command to rebuild the boot configuration data. You can also run the bootrec command with the following switches:

  • /fixmbr: Repairs the master boot record

  • /fixboot: Repairs the boot sector

  • /rebuildbcd: Rebuilds the boot configuration data

Drive not Recognized by the BIOS/UEFI

HDD/SSD

A modern BIOS/UEFI automatically detects your drives and their geometry during POST. In older systems, you had to manually enter the disk geometry and it was very common for a wrong value to be entered. In modern systems, this rarely happens. If the BIOS can't detect your drive, it's usually caused by one of three things.

• The power connector is unplugged.

• The SATA cable is unplugged.

• The drive is malfunctioning.

Application Crash

If an application you are using crashes, an error has occurred that gives you no choice except to exit the application. Sometimes you can fix the problem by rebooting the computer. You may need to debug your system. Check log files for errors that provide clues about what might have caused the crash.

Crash Screens

If you experience a Blue Screen of Death (BSOD) on a Windows machine or Spinning Pinwheel of Death (SPOD) on a MAC, several events may have occurred. You could have a fatal system error that is preventing the system from operating safely, or just one application may have failed. Often, rebooting the computer solves the problem. If that doesn't work, you can attempt to revert the system to a previous state to undo any software or hardware changes that are causing problems. Scan your computer for viruses, roll back drivers, update drivers, update your operating system, update BIOS or return them to their factory settings, repair permissions, or clear the dyld cache.

Drive Noise

HDD

Excessive or unusual drive noise is almost always indicative of a failing hard disk. For example, a clicking noise coming from the drive usually indicates one or more failing heads.

Optical MediaCharacteristics

Compact Disc
(CD)

CDs were first developed to store digital music. Later, the CD technology was adapted to store digital computer data. A CD:

• Can hold 74 to 80 minutes of audio.

• Is 120 millimeters in diameter.

• Is 1.2 millimeters thick.

CD-ROM stands for compact disc read-only memory. CD-ROMs are identical in appearance to audio CDs. CD-ROMs store and retrieve data in a very similar manner to CDs. CD-ROMs:

• Have lands and pits; they use reflective light to interpret the data on the disc.

• Hold about 737 MB of data with error correction (847 MB total).

• Transfer data at a rate of 150 KBps.

  • Drive speeds are measured as multiples of this original speed.

  • To calculate an estimate of a CD-ROM drive transfer rate, multiply its speed by 150 kilobytes (1x = 150 KBps, 2x drive = 300 KBps, 4x drive = 600 KBps, 72x = 10,800 KBps).

CD-RW stands for compact disc rewritable.

• A CD-RW disc:

  • Can be written to. It can be read, erased, and rewritten many times.

  • Has a capacity of approximately 650 MB.

  • Is a removable hard drive. You can insert the disc into the disc drive on one PC; add and delete data; and eject it. You can insert it into another disc drive on another system with all the data immediately accessible.

• A CD-RW drive:

  • Can burn (write to) CD-RW discs, read CD-RW discs, erase CD-RW discs, and read a CD-ROM disc.

    • CD-RW drive speed rating includes three parameters: a write speed, a rewrite speed, and a CD-RW read speed.

    • The parameters are multiples of the original 150 KBps 1x speed defined by the first CD-ROM drives.

    • For example, if you have an 8x4x32 CD-RW drive, this means that it can write at 1,200 KBps, it can rewrite to a CD-RW disk at 600 KBps, and it can read at 4,800 KBps.

  • Has the bottom surface coated with a photo reactive crystalline coating. A red laser causes a crystal to form which creates the reflective and non-reflective areas on the bottom of the CD-RW disc.

  • Has a second, high-power write laser. When this laser hits the bottom of the photo reactive material on the bottom of the CD-RW disc, it causes crystals to form. This is called phase shifting or a phase shifting media. A crystal forming on the bottom of a CD-RW disc is like a land on a CD-ROM disk, it reflects light.

Digital versatile disc
(DVD)

A DVD is an optical media standard that can be used to store large amounts of different types of data, such as computer data, video, and audio. Most DVD drives can read and write.

• A DVD with a single side of data can hold about 4.7 GB.

• A DVD-ROM is read-only memory.

• DVD-R (recordable) can be recorded only once. It is supported by older drives or older DVD players.

• DVD-RW is a rewritable DVD format.

  • DVD-RW uses a crystal encoding on the bottom of the DVD disc.

  • A DVD-RW DL (dual-layer) employs two recordable dye layers, each capable of storing about 4.7 GB; the total disk capacity is 8.5 GB.

    • The outer layer is semi-transparent, allowing the laser to read data from the inner layer.

    • Dual-layer discs can hold up to 8.5 GB of data.

    • Dual-layer recordable discs cost more than single layer discs.

    • Dual-layer DVDs are recorded using Opposite Track Path (OTP).

    • Most newer drives can read both single and dual layer discs. However, older drives might not support dual-layer discs.

• DVD speeds use a multiple of 1.35 MBps (1x = 1.35 MBps, 2x = 2.7 MBps, etc.) or 11 Mbps (1x = 11 Mbps, 2x = 22 Mbps, etc.).

Blu-ray disc
(BD)

Blu-ray Disc is a newer optical disc format that is capable of greater storage capacity than DVDs.

• Blu-ray was originally developed for high-definition video (and expanded content on movie discs), but can also be used for data storage.

• Blu-ray uses a blue laser instead of the red laser used with CDs and DVDs. The blue laser light has a shorter wavelength, which allows data to be packed more tightly on the disc.

• A single layer Blu-ray disc holds 25 GB; a double layer disc holds up to 50 GB. Experimental 20 layer discs can hold up to 500 GB.

• Blu-ray discs can be read-only (BD-ROM), recordable (BD-R), or rewritable (BD-RE).

• A 1x Blu-ray drive reads data at 4.5 MBps.

• Most Blu-ray drives include a second read laser for reading CDs and DVDs. Without this additional laser, Blu-ray drives would not be able to read CDs or DVDs.

• Blu-ray is intended to eventually replace DVD.

• Blu-ray has become the accepted HD video standard; the last movie studio stopped distributing HD DVD movies.