5.4 RAID

You have been asked to implement a RAID 5 solution for an engineer's desktop workstation. What is the minimum number of hard disks that can be used to configure RAID 5? 2 3 4 5 6

3 A RAID 5 array stripes data and parity information across multiple hard disks. To complete a RAID 5 array, a minimum of three hard disks is required. RAID 0 and RAID 1 can both be implemented with a minimum of two hard disks.

Which of the following drive configurations uses striping with parity for fault tolerance? RAID 1 RAID 0 RAID 10 RAID 5

RAID 5 RAID 5 also uses disk striping, but provides fault tolerance for a single disk failure. Disk striping breaks data into units and stores the units across a series of disks by reading and writing to all disks simultaneously. RAID 0 uses disk striping and offers no fault tolerance. A failure of one disk in the set means all data is lost. RAID 1 provides fault tolerance, but does not use striping. A RAID 10 array nests a mirrored array within a striped array.

Operating System RAID

Operating system RAID uses RAID features within the operating system. Like software RAID, the system CPU is used for RAID operations, but performance is typically better than software RAID because of integration with the operating system.

Striping

(Stripe-ing)

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 is due to mirroring. > Requires a minimum of four disks.

Redundant Array of Independent Disks (RAID)

A disk sub-system that combines multiple physical disks into a single logical storage unit. * A way of storing the same data in different places on multiple hard disks or solid-state drives (SSDs) to protect data in the case of a drive failure.

Basic Disk Storage

Available in DOS and Windows versions Primary/extended partitions, logical drives Basic disk partitions can't span separate physical disks Operations to be performed: * Create and delete primary and extended partitions. * Create and delete logical drives within an extended partition. * Format a partition and mark it as active. * They are compatible with older operating system. * A basic disk can be easily converted to a dynamic disk without losing any data.

How do RAID 5 and RAID 10 differ?

In RAID 5, data is divided equally in all disks. In RAID 10, data is stored in one disk and mirrored in another disk for security of data. 2. It emphasis on data storage.

A computer being used by the HR department needs to ensure that all of the data on that computer is protected from a single hard disk failure. The data needs to be read as quickly as possible, and the HR department would like to maximize drive use as much as possible. This computer can use up to three hard drives. Which of the following RAID types would meet these requirements and provide the BEST data protection? RAID 0 RAID 1 RAID 5 RAID 10

RAID 5 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. RAID 5 also provides an increase in performance for read operations. With three drives, RAID 5 uses approximately 33% overhead, whereas RAID 1 and 10 use 50%. RAID 0 does not provide fault tolerance. If one disk in the set fails, all data is lost. RAID 10 requires a minimum of four disks; this computer only has three.

What is an advantage of RAID 5 over RAID 1? RAID 5 continues to operate with a failure in two disks; RAID 1 can only operate with a failure of one disk. RAID 5 improves performance over RAID 1. RAID 5 provides redundancy for the disk controller. RAID 5 provides redundancy; RAID 1 does not.

RAID 5 improves performance over RAID 1. RAID 5 provides both fault tolerance and improved performance. RAID 1 (mirroring) provides only fault tolerance with no performance benefit. Both RAID 5 and RAID 1 can only sustain a loss of one disk in the set. Use multiple disk controllers to provide redundancy for the disk controller.

What is the minimum number of disks required for a RAID 5 configuration?

RAID 5 is the most common secure RAID level. It requires at least 3 drives but can work with up to 16.

redundency

Redundancy means having extra or duplicate resources available to support the main system. It is a backup or reserve system that can step in if the primary system fails. The reserve resources are redundant most of the time as they are not being used if everything is working properly.

Overhead

Refers to the processing time required by system software, which includes the operating system and any utility that supports application programs.

Software RAID

Software RAID uses a driver and the system CPU for controlling RAID operations. This is the slowest form of RAID. * Some RAID controller cards support RAID configuration, but without the onboard RAID processor. These solutions are classified as software RAID (sometimes called fake RAID) even though you install a controller card to provide RAID capabilities. * Many motherboards include built-in (onboard) support for RAID. RAID implemented in this way is typically software/driver RAID. * Software RAID uses a driver and the system CPU to control RAID operations. This is the slowest form of RAID.

How do striping and mirroring differ?

Stripping breaks the data into units and stores it across several disks while mirroring duplicates the data on multiple disks

Another term that is sometimes used with disk arrays is JBOD (just a bunch of disks). JBOD is not a RAID configuration, but like RAID, configures multiple disks into a single logical storage unit.

* A JBOD configuration creates a single volume using space from two or more disks. * Spanning is another term for JBOD because the volume spans multiple physical disks. * Data is not striped between disks, but saved to one or more disks (depending on how the operating system decides to save each file). On a new JBOD configuration, data is typically saved to the first disk until it is full. Then additional data is saved to the second disk and so on. * Disks used within the spanned volume can be of different sizes. * JBOD uses the entire space available on all disks for data storage (no overhead). * There are no performance or fault tolerance benefits with JBOD. * If one drive fails, you might be able to use disk recovery tools to recover data from the remaining disks.

The process for installing RAID hardware depends on your motherboard. You will need to locate manufacturer directions to learn how to install RAID on your hardware. There are several ways to implement RAID:

* Hardware * Software * Operating System

Be aware of the following facts about RAID:

* Some RAID controllers support combined levels of RAID. For example, RAID 0+1 is a striped array that is mirrored. Other combined configurations that might be supported include RAID 1+0 (also called RAID 10), RAID 5+0, and RAID 5+1. * For all RAID configurations, the amount of disk space used on each disk must be of equal size. If disks in the array are of different sizes, the resulting volume will be limited to the smallest disk. Remaining space on other drives can be used in other RAID sets or as traditional storage. * While some RAID configurations provide fault tolerance in the event of a disk failure, configuring RAID is not a substitute for regular backups.

What is parity?

Parity is where the system uses striping on three or more disks that can be used for data reconstruction if one of the disks fails * A method in which the computer ensures the data it processes is accurate.

You have been asked to configure the drives in a computer. The end user wants to use striping without incorporating any fault tolerance. Which of the following will BEST meet these requirements? RAID 5 Expanded volume set RAID 0 RAID 1

RAID 0 RAID 0 uses disk striping and offers no fault tolerance. Disk striping breaks data into units and stores the units across a series of disks by reading and writing to all disks simultaneously. A failure of one disk in the set means all data is lost. This is the fastest of all RAID types. RAID 5 also uses disk striping, but provides fault tolerance for a single disk failure. RAID 1 provides fault tolerance, but does not use striping. An expanded volume set is a volume that spans more than one hard drive. An expanded volume set also offers no fault tolerance, yet does not use striping.

Just a Bunch of Disks (JBOD)

A configuration that places multiple disks in a single logical storage unit. > A disk arrangement in which two or more disks are abstracted to appear as a single disk to the OS but aren't arranged in a specific RAID configuration.

Multiboot COnfiguration

A dual boot is a technique through which multiple operating systems can be kept within the boot sequence on the same computer. It enables a user to select from more than one operating system at the initial boot sequence or system startup. Dual boot is also known as multi boot.

One of the video editors in your company is worried that he may lose a lot of data if his hard drive fails. He has asked you to come up with a solution. To do this, you have decided to implement a RAID 10 solution on his desktop workstation. Which of the following is the MINIMUM number of hard disks that can be used? 2 3 4 5 6

4 A RAID 10 array nests a mirrored array within a striped array. To create a RAID 10 array, a minimum of four hard disks is required (two for the mirrored array and two more to stripe the mirror).

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.

Dynamic Disk

A disk that has been initialized for dynamic storage is called a dynamic disk. It gives more flexibility than a basic disk because it does not use a partition table to keep track of all partitions. The partition can be extended with dynamic disk configuration. It uses dynamic volumes to manage data. * Create and delete simple, spanned, stripped, mirrored, and RAID-5 volumes. * Extend a simple or spanned volume. * Repair mirrored or RAID-5 volumes. * Reactivate a missing or offline disk. * They are supported by windows 2000 and above. * In dynamic disk, there is no partition and it contains simple volumes, spanned volumes, stripped volumes, mirrored volumes, and RAID-5 volumes. * It does not support multi-boot configuration.

MTBF (Mean Time Between Failures)

A measure of the average time between failures in a system - the higher the amount, the more reliable the thing is.

Hardware RAID

A method of implementing RAID that relies on an externally attached set of disks and a RAID disk controller, which manages the RAID array.

RAID 1 (Mirroring)

A mirrored volume stores data to two duplicate disks simultaneously. If one disk fails, data is present on the other disk, and the system switches immediately from the failed disk to the functioning disk. Mirroring: * Provides fault tolerance for a single disk failure. * Does not increase performance. * Requires two disks. * Has a 50% overhead. Data is written twice, meaning that half of the disk space is used to store the second copy of the data. Overhead is 1 / n where n is the number of disks. * RAID 1 is the most expensive fault tolerant system.

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. * Increases the risk of performance but drastically increases the risk of data loss

Array

An array is a data structure that holds similar, related data. An array is like a collection of boxes, each of which is called an element . Each element has a position in the array, and can hold a value. The data in an array must all be of the same data type .

How does a RAID 0 configuration improve disk read and write performance?

By dividing data into blocks and spreading them across multiple drives using what is called disk striping. By spreading data across multiple drives, it means multiple disks can access the file, resulting in faster read/write speeds.

You are running Windows 10 on your computer. You want to decrease the time it takes to write data to your drives. To do this, you have decided to create a Windows software RAID system using a striped volume. Before you create the striped volume, which action MUST you take? Use a multi-partition volume on a basic disk. Convert basic disks to dynamic disks. Format your disks to use GPT partitions. Format your disks to use MBR partitions.

Convert basic disks to dynamic disks. When creating a Windows software RAID on Windows 10, all of the drive used for the RAID system must be configured as dynamic disks. The step of formatting your disks comes after the step of configuring your drives as either basic or dynamic. Like basic disks, dynamic disks can use the MBR or GPT partition styles on systems that support both. With older versions of Windows, a basic disk included a multi-partition volume. To encourage the use of dynamic disks, multi-partition volume support was removed from basic disks and is now exclusively supported on dynamic disks.

You have a computer with three hard disks. A RAID 0 volume uses space on Disk 1 and Disk 2. A RAID 1 volume uses space on Disk 2 and Disk 3. Disk 2 fails. Which of the following is true? Data on the RAID 0 volume is accessible; data on the RAID 1 volume is not. Data on both volumes is not accessible. Data on both volumes is still accessible. Data on the RAID 1 volume is accessible; data on the RAID 0 volume is not.

Data on the RAID 1 volume is accessible; data on the RAID 0 volume is not. In this scenario, Disk 2 is shared between both volumes. If Disk 2 fails, the RAID 1 volume is still accessible because RAID 1 (mirrored) volumes can sustain a loss of a single disk. The data on the RAID 0 volume is not accessible. RAID 0 uses striping, which distributes the data evenly between multiple disks. If a single disk fails, the entire volume is lost.

You have an existing computer running Windows 10. You want to configure a RAID 1 array in the computer. You install two new SATA drives, then use the RAID controller integrated in the motherboard to define a RAID 1 array using them. When you boot the computer, Windows does not show the logical RAID drive. What should you do? Install the drivers for the RAID controller. In the BIOS, change the SATA disk mode to RAID. In the BIOS, change the SATA disk mode to AHCI. Set the jumpers on the drives to use SATA I mode.

Install the drivers for the RAID controller. You must install the RAID driver so that Windows recognizes arrays created by the motherboard RAID utility. Without the driver, Windows will not be able to see the logical drive defined by the array. When you define the array, you configure the BIOS to use RAID as the SATA type. If you had not completed this step, you would not be able to run the RAID configuration utility. Use AHCI to configure SATA drives to support hot swapping.

You are configuring a new system, and you want to use a RAID 0 array for the operating system using SATA disks and the RAID functionality built into the motherboard. Which of the following BEST describes the action you will take as part of the configuration? In the BIOS, set the disk mode to IDE. Load the RAID drivers during operating system installation. Set master/slave jumpers on the hard drives. Set the disk mode to AHCI in the BIOS.

Load the RAID drivers during operating system installation. If you are using an onboard RAID controller with SATA drives, edit the CMOS settings and identify the drive type as RAID. This tells the system to load the onboard BIOS for accessing the connected drives. If you want to install the operating system on a RAID array, you need to manually load the controller driver so that Windows can see the RAID array.

What advantages does RAID 5 have over RAID 1?

No need of large space, supports data accessing at the time of recovery and high security of data. RAID 5 is generally suited for medium level of applications. RAID 5 was introduced to make the random write performance better.

You are building a new computer that will contain two hard disks. To provide increased performance, you have decided to configure the drives using RAID technology. Which of the following will BEST meet your needs? RAID 5 RAID 1 RAID 2 RAID 0

RAID 0 RAID 0 (striping) uses two or more disks and provides an increase in performance, but not fault tolerance. RAID 1 (mirroring) uses two disks to provide fault tolerance, but not an increase in performance. RAID 5 uses a minimum of three disks and provides both fault tolerance and an increase in read performance.

With a RAID 0 configuration, what happens to your data if a drive in the set fails?

RAID 0 (disk striping) does not provide any protection against drive failures. If one or more drives fail, all of the information contained on the volume becomes totally inaccessable.

Ben is concerned about losing data due to a hard disk failure. His computer will only support a maximum of three disks. To protect his data, you have decided to use RAID (redundant array of independent disks). Which of the following RAID types would give Ben the BEST mirrored data protection? RAID 0 RAID 1 RAID 5 RAID 10

RAID 1 RAID 1 is the only mirrored solution that can work on three or less drives. RAID 0 and RAID 5 protects data using stripping. RAID 10 uses mirroring, but requires a minimum of four disks.

One of your customers wants you to build a personal server that he can use in his home. One of his concerns is making sure he has at least one backup of their data stored on the server in the event that a disk fails. You have decided to back up his data using RAID. Since this server is for personal use only, the customer wants to keep costs down. Therefore, he would like to keep the number of drives to a minimum. Which of the following RAID systems would BEST meet the customer's specifications? RAID 0 RAID 1 RAID 5 RAID 10

RAID 1 RAID 1 will protect memory from a single disk failure and provides high-read performance. It also only requires a minimum of two disks. RAID 5 would also protect data from a single disk failure, but requires a minimum of three disks, and RAID 10 requires a minimum of four disks.

You work for a small company as the human resources specialist. Since the company is fairly small, you are maintaining all of the employee information on your desktop computer, which is running Windows 10. This computer has two high-capacity hard disks. You want to ensure that this information is protected from a hard disk failure, so you want to set up a Windows software RAID system. Which of the following would be your BEST solution? Use spanned volumes. Use mirrored volumes. Use striped volumes. Use RAID 5 volumes.

Use mirrored volumes. A Windows software RAID system can be configured in Windows 10 using the Windows Disk Management tool. Of the available options from within Disk Management, you would need to configure a mirrored volume to protect your data from a disk failure. Disk mirroring requires two available drives with sufficient storage. Once configured, the data written to a mirrored volume is duplicated to both drives. This duplication, or mirroring, means that if one of the mirrored drives fails, all of the data can still be retrieved from the remaining good drive. A spanned volume is a dynamic volume consisting of disk space on more than one physical disk. This method does not duplicate the data. If a spanned volume drive fails, the data is lost. A striped volume uses the free space on more than one physical hard disk to create a bigger volume similar to a spanned volume. However, a striped volume writes across all volumes in the stripe in small blocks, distributing the load across the disks in the volume. In other words, when a single file is written, some of the file will be on one disk, and the rest of the file will be on another disk. This makes writing files faster as the data to all of the disks in the strip at the same time. It does not, however, protect the data in the event of a disk failure.