by MS
Disk List view Provides summary information about physical drives. This information includes the disk number and device type, such as basic, removable, or CD-ROM; the disk capacity; the size of unallocated space on the disk (if any); the status of the disk device, such as online or offline; and the device interface type, such as integrated device electronics (IDE), small computer system interface (SCSI), universal serial bus (USB), or FireWire (1394).
You can change the view for the top or bottom pane using options from the View menu. To change the top view, select View, choose Top, and then select the view you want to use. To change the bottom view, select View, choose Bottom, and then select the view you want to use.
As you can see, the available views provide overviews of available disks. To get more detailed information on a local disk, right-click it in any of Disk Management's views and then select Properties. When you do this, you'll see a dialog box much like the one shown in Figure 9-3. This is the same dialog box that you can access from Windows Explorer (by right-clicking the top-level icon for the drive and then choosing Properties).
Figure 9-3: Examine detailed information for a drive using its Properties dialog box.
Using FSUtil and DiskPart
Windows Vista provides several command-line tools for working with disks, including the following:
FSUtil Meant to be used by support professionals who need to manage disks at a fairly low level. Using FSUtil, you can examine and work with meta-information related to disks and the information they contain, including update sequence number (USN) change journals, reparse points, and hard links. You can also obtain detailed sector and cluster information, such as the number of free or reserved sectors on a disk. To learn more about FSUtil, type fsutil help at an elevated command prompt.
DiskPart A text-mode command interpreter that you can use to manage disks, partitions, and volumes from the command prompt. Not only can DiskPart perform many of the same operations as Disk Management, but it can also be used with scripts to automate disk management processes. You start DiskPart by typing diskpart at an elevated command prompt. You will then be at the DISKPART> prompt. If you type help and press Enter, you will see a list of available commands and a description of their usage.
Note
Unlike Disk Management, which provides a friendly interface and is fairly easy to use, FSUtil and DiskPart are complex tools meant for advanced administrators. Their use is covered in detail in Microsoft Windows Command-Line Administrator's Pocket Consultant (Microsoft Press, 2004). You'll find a detailed example of using DiskPart in the "Marking a Partition as Active" section of this chapter.
Improving Disk Performance
Windows Vista has several features that affect how disks are used. These include:
Windows ReadyBoost Boosts system performance by using USB flash devices as additional sources for caching
Windows ReadyDrive Boosts system performance on mobile computers equipped with hybrid drives
Windows SuperFetch Boosts system performance using a modified memory management algorithm
Each of these features is discussed in the sections that follow.
Understanding and Using Windows ReadyBoost
A computer's disk drives aren't just used for reading and writing application data and user documents. The operating system makes extensive use of a computer's disk drives for paging files and system cache. Because it's significantly slower to read from and write to a disk than it is to read from and write to physical memory (RAM), this can cause a bottleneck that degrades performance. Windows Vista introduces Windows ReadyBoost as a way to reduce the performance impact related to reading and writing the system cache.
With Windows ReadyBoost, USB flash devices with sufficiently fast memory are used to extend the disk caching capabilities of the computer's main memory. Using flash devices for caching allows Windows Vista to make random reads faster by caching data on the USB flash device instead of a disk drive. Because this caching is applied to all disk content, not just the page file or system dynamic-link libraries (DLLs), the computer's overall performance is boosted because flash devices can be read up to 10 times faster than physical disk drives.
USB flash devices that can be used with Windows ReadyBoost include USB 2.0 flash drives, Secure Digital (SD) cards, and CompactFlash cards. These devices must have sufficiently fast flash memory and be at least 512 MB or larger in size. If the flash device has both slow and fast flash memory, only the fast flash memory portion will be used for boosting performance. Windows Vista can use an amount of flash memory equal to twice the amount of physical memory (RAM) on the computer.
Memory on USB flash devices is primarily used for random input/output (I/O), because most flash devices are slower than a disk drive for sequential I/O. Windows ReadyBoost maximizes performance by automatically passing large, sequential read requests to the computer's disk drive for servicing. To allow a USB flash device to be removed at any time, all data writes are made to the hard disk before being copied to the flash device. This means all data stored on the flash device is duplicated on the hard disk and there is no potential for data loss when removing the flash device. Additionally, because the flash device's memory may contain sensitive information, Windows ReadyBoost encrypts the data so it can only be used with the computer on which it was originally written.
Enabling ReadyBoost
With Windows ReadyBoost, USB flash devices with sufficiently fast flash memory can be used as additional sources of system cache. The following steps detail how Windows ReadyBoost works the first time you use a USB flash device with a computer:
When you insert a USB flash device into a USB 2.0 or higher port, Windows Vista analyzes the speed of the flash memory on the device. If the flash memory performs at a sufficiently high speed, the computer's physical memory can be extended to the USB flash device. In most cases, you'll want the flash memory to be at least as fast as the computer's bus speed.
The AutoPlay dialog box, shown in Figure 9-4, should be displayed automatically. If you want the device to always be used with Windows ReadyBoost when inserted, select the Always Do This… check box. Because you've selected the Always Do This… option, the AutoPlay dialog box will not be displayed the next time you insert the device (unless you change the AutoPlay defaults in Control Panel).
Figure 9-4: Select the Speed Up My System Using Windows ReadyBoost option.
When you click Speed Up My System Using Windows ReadyBoost, Windows Vista extends the computer's physical memory to the device. The default configuration enables Windows ReadyBoost to reserve all available space on the device for boosting system speed.
Note
Windows Vista can use an amount of flash memory equal to twice the amount of physical memory (RAM) on the computer. If a device has both fast and slow flash memory, Windows Vista only uses the fast portion of the memory.
To use Windows ReadyBoost with a USB flash device that you either already inserted or that you previously declined to use with Windows ReadyBoost, follow these steps:
Click Start and then click Computer.
Right-click the USB flash device in the Devices With Removable Storage list and then choose Properties.
On the ReadyBoost tab, select Use This Device and then click OK.
For USB flash devices that do not support ReadyBoost, you cannot enable the device. The only option you'll have is to stop retesting the device when you plug it in. The Stop Retesting This Device When I Plug It In option is selected by default.
Configuring ReadyBoost
Windows ReadyBoost can be used in a variety of configurations. You do not have to configure the computer to use all available space on the USB flash device. You can also configure a specific amount of space to reserve. To do this, follow these steps:
Click Start and then click Computer.
Right-click the USB flash device in the Devices With Removable Storage list and then choose Properties.
On the ReadyBoost tab, use the Space To R
eserve For System Speed slider or combo box to set the amount of space to use with ReadyBoost. If you reserve less than the total amount of space available, the free space can be used for files and data.
Click OK.
Ejecting a USB Flash Device That Uses ReadyBoost
You can safely remove a USB flash device that uses ReadyBoost at any time without losing data or negatively impacting the system. However, when the device is removed, the system performance returns to its normal level—the performance level experienced without the device. To remove the device, follow these steps:
Open Windows Explorer or another Explorer view, such as Computer.
Right-click the device and then select Eject or Safely Remove.
Understanding and Using Windows ReadyDrive
Windows ReadyDrive improves performance on mobile computers equipped with hybrid drives. A hybrid drive is a drive that uses both flash RAM and a physical drive for storage. Because flash RAM is much faster than a physical disk, mobile computers running Windows Vista write data and changes to data to the flash memory first and periodically sync these writes and changes to the physical disk. This approach reduces the spinning of the physical drive and thus saves battery power.
The flash RAM on hybrid drives can be used to provide faster startup and resume from sleep or hibernation. In this case, the information needed for starting or resuming the operating system is written to the flash RAM prior to shutting down, entering sleep, or going into hibernation. When you start or wake the computer, this information is read from the flash RAM.
You do not need to enable ReadyDrive. ReadyDrive is enabled for use automatically on mobile computers with hybrid drives.
Understanding and Using Windows SuperFetch
Windows Vista improves performance and responsiveness by changing the way user processes and background processes are used. In Windows XP, user processes and background processes have the same memory use prioritization: User processes and background processes are both loaded into memory as they are used. Because there is no prioritization, there often is contention for memory, and there are often performance lags as well because after background processes run, they remain resident in memory. Therefore, data for user applications and processes must be loaded into memory when they are requested. Windows Vista corrects this issue by ensuring that background processes are unloaded after they run and when data for user processes is reloading into memory.
In Windows XP, user processes and background processes have the same I/O priority, which often results in conflict and poor read/write performance. Windows Vista corrects this by implementing high priority I/O and low priority I/O queues. High priority I/O is used for user process and application reads and writes to physical drives. Low priority I/O is used for background process reads and writes to physical drives.
Note
With Windows Vista, many services and routine housekeeping tasks run as background processes. For example, on Windows Vista, Disk Defragmenter is scheduled to run automatically to periodically defragment disks. When Disk Defragmenter runs, it runs as a background process and uses low priority I/O.
The key feature that makes memory and I/O prioritization work is Windows Super-Fetch. Windows SuperFetch improves system performance using a modified memory management algorithm. Unlike the memory management algorithm in Windows XP and earlier versions of Windows, SuperFetch optimizes memory usage based on the way the current user is using the computer. SuperFetch does this by performing the following tasks:
Differentiating between user applications and background services running on the computer SuperFetch makes the computer more responsive to user requests by prioritizing the current user's processes over background tasks. Because user processes always have priority over background tasks, background tasks do not take up all the processor time and the system remains responsive to user requests.
Optimizing memory for users after running background tasks Housekeeping tasks on Windows Vista make better use of process idle time than earlier versions of Windows do. More system and maintenance tasks, such as Disk Defragmenter and Disk Backup, run during idle time. When the computer is idle, background processes run as they normally would. However, when background processes end, SuperFetch repopulates memory to the state it was in prior to running the background processes. This ensures memory is optimized for user processes and the computer is responsive to user requests.
Tracking the most frequently-used applications and anticipating user needs SuperFetch keeps track of which applications users run most frequently and also tracks when those applications typically are used. SuperFetch then uses the tracking information to preload the application and ready it for use when it expects that the user will need the application. This ensures faster startup for applications and faster user switching over time.
Taking advantage of Windows Vista's low priority I/O designation SuperFetch takes advantage of Windows Vista's high priority I/O and low priority I/O queues to improve read/write times for user processes and improve a computer's overall responsiveness. When multiple processes are competing for I/O, high priority processes always get more I/O time than low priority processes do. As a result, user processes and applications have better performance, and there is less contention for I/O time when both user processes and background processes are running.
As an administrator, you should understand not only how SuperFetch works but also the way it is configured. All versions of Windows Vista support SuperFetch. Some basic characteristics of SuperFetch follow.
Runs as a service named SuperFetch. This service runs automatically at startup and logs on using the Local System account.
Uses the SvcHost.exe executable, running in a network restricted mode. This means SuperFetch can only access the local computer and doesn't have access to any networks to which the computer might be connected.
Depends on the Filter Manager component for proper operations. Filter Manager provides file information and file system information needed by SuperFetch, and it is installed automatically with the operating system.
Writes prefetch data to the %SystemRoot%prefetch folder. The prefetch data is used to quickly start applications. Within the prefetch folder, you'll also find several database files used to track application usage history and to speed up application performance. Application faults are also tracked in a database history file.
Working with Basic and Dynamic Disks
Not that long ago, all Windows computers shipped with their hard disks configured as basic disks. Now, because people want larger or more robust disks, computer manufacturers have responded by increasingly shipping computers with their hard disks configured as dynamic disks. Instead of having a single 120 gigabyte (GB) drive, a new computer might have a spanned disk with 360 GB, where three 120 GB drives act as a single local disk. In this scenario, disk spanning is used to make multiple disks appear to be a single disk, and the primary way to implement this on Windows Vista is to use dynamic disks. In other words, you can no longer take for granted that a new computer (or any computer, for that matter) has a basic disk. The only way to be sure of the disk type is to check Disk Management; all the views show the disk type.
As more and more computers are shipped with dynamic disks, you might wonder whether your computers using basic disks should be converted to dynamic disks. In some cases, the need for standardization might prompt your decision. For example, for better manageability, you might want all desktops in a particular department to have the same configuration. In other cases, IT management might direct the change, because the conversion from basic disks to dynamic disks can be considered an upgrade process. (That is, you are moving computers from an older disk type to a newer disk type.) However, before you decide to move from one disk type to another, you should understand what is involved, what features are supported, and what features are not supported.
A basic disk is a physical disk that has one or more basic volumes that can be configured as primary partitions, extended pa
rtitions, and logical drives. A primary partition is a drive section that you can access directly for file storage. Each physical drive can have up to four primary partitions. You make a primary partition accessible to users by creating a file system on it. In the place of one of the four permitted primary partitions, you can create an extended partition (meaning the basic disk could have up to three primary partitions and one extended partition). Unlike primary partitions, you can't access extended partitions directly. Instead, you can configure extended partitions with one or more logical drives that are used to store files. Being able to divide extended partitions into logical drives enables you to divide a physical drive into more than four sections. For example, you could create logical drives F, G, and H in a single extended partition.
A dynamic disk is a physical disk that has one or more dynamic volumes that can be configured as simple, spanned, or striped volumes. Unlike a basic disk, a dynamic disk can have an unlimited number of volumes—any one of which can be extended or used as a system volume. Although basic disks can be used with any Windows-based operating system, dynamic disks can be used only with Windows 2000 or later and are incompatible with earlier versions of Windows. As an example, this means that if Disk 0 is a dynamic disk, you would not be able to boot that disk to Windows 98.
A key advantage of dynamic disks is the capability to combine physical disks using the spanning or striping feature of Windows Vista. When you span or stripe drives, you create a single dynamic volume that extends from one disk to other disks, using all or part of each disk in the set. The difference between spanning and striping is in how data is written. With spanning, Windows Vista recognizes spanned disks just as it would a single partition, and writes to the spanned disk are written to the entire partition randomly. With striping, Windows Vista writes a portion of the data to each of the underlying disks that make up the volume. In most cases, striping gives you faster read/write access to data because data is read from and written to multiple disks.