Windows XP Disk Devices and Disk Management

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Windows XP Disk Management is available under the Computer Management console. Disk Management replaces the Windows NT 4.0 Disk Administrator. It offers many new features to Windows XP. These include:

• Support for basic partitions (both primary and extended with logical drives), and dynamic volumes (mirroring, extended)

• Online disk management that allows changes to be made without having to shut down the system. Most changes take place automatically.

• Local and remote administration of disks

• Shortcut menus and wizards to make the process simpler.

• The only considerations that need to be addressed are the following:

• You must be a member of the Administrators group.

• Dynamic disks and volumes are not supported on portable computers.

The console window will show you a graphical view of your system's disk configuration. To view remote systems, you must create a new console and add the Disk Management snap-in, connecting to the remote system.

Configuring Disks
Windows XP supports both basic and dynamic storage. Each of these provides specific capabilities and restrictions.

Basic Storage
Basic storage consists of primary and extended partitions. Any one physical drive can have up a total of four partitions. You must have one primary partition, and you can have up to four primary partitions. You can have only one extended partition per physical hard drive. Logical drives are used to divide the extended partition into smaller chunks of workable drive space.

Using Disk Management, you can still create partitions on a basic disk, but you will no longer need to commit changes to save them, or restart your computer to implement them, as you did with Windows NT 4.0. Any changes made by Disk Management are implemented immediately. However, under Windows XP, you can no longer create volume sets or stripe sets on a basic disk, although it will support these sets if they are already in place prior to upgrading to Windows XP. You also can no longer extend volumes or volume sets on a basic disk.

The following are the tasks that can be performed on a basic disk:
• Create and delete primary and extended partitions.
• Create and delete logical drives within an extended partition.
• Format a partition.
• Mark a partition as active.
• Delete volume sets and striped sets (Windows XP upgraded from Windows NT)
• Repair and delete mirror sets and stripe sets with parity (Windows 2000 Server upgraded from Windows NT Server).

Dynamic Storage
Dynamic storage is a new feature in Windows XP. It is a physical disk that has been upgraded by and managed with Disk Management. Dynamic disks do not use partitions or logical drives, but rather dynamic volumes, which must be created by Disk Management. Only computers running a Windows XP operating system can access these dynamic volumes locally. However, any operating system (such as Windows 95 or Windows NT 3.51 Workstation) can access these volumes through a network share. Dynamic disks are not supported on portable computers or removable media.

Dynamic volumes can only be created on dynamic disks. With dynamic disks, the four-volume limitation of basic storage is removed. You can create any number of volumes on the dynamic disk; the only limit is free space.

There are five types of dynamic volumes: simple, spanned, mirrored, striped, and RAID-5. Windows XP can only use simple, spanned, and striped volumes. However, you can still create mirrored and RAID-5 volumes remotely on a Windows 2000 Server.

The following tasks can only be performed on a dynamic disk:
• Create and delete simple, spanned, and striped volumes.
• Extend a simple or spanned volume.
• Reactivate a missing or offline disk
• Create, repair, and delete mirrored and RAID-5 volumes (remotely to Windows 2000 Server).

NOTE: You cannot expand the boot or system volumes. This is because neither can be on a spanned volume, and Windows XP recognizes an expanded volume as a spanned volume.

To upgrade a basic disk to a dynamic disk, select the disk (not the volumes). From there, either use the Action Menu | All Tasks, or right click the disk, and choose Upgrade to Dynamic Disk. The system will then prompt you to select which disks to upgrade, allowing you to upgrade several disks at once.

NOTE: When upgrading from basic to dynamic disk, keep in mind that the entire physical disk must be upgraded from basic to dynamic. You cannot upgrade a single partition. Upgrading is a one-way process. You can convert to dynamic disk from basic disk with no setup or data loss, but to revert back to basic disk will require the entire disk to be reformatted.

Configuring Volumes
Each of the two types of disk storage (basic and dynamic) supports their own distinct types of volumes. A basic storage disk behaves just like in Windows 95 or MS-DOS. A dynamic storage disk behaves similar to the RAID configurations of Windows NT.

Basic Volumes
Under Windows XP, basic volumes are used to provide compatibility with other operating systems (such as in a dual boot configuration). Basic volumes do not make any change to the structure and handling of drives and volumes from previous versions of Windows and Windows NT.

Basic volumes must exist on a basic disk. You are limited to 4 partitions on each drive. One of these partitions can be created as an extended partition, which can host logical drives.

When you upgrade to Windows XP, any existing partitions will change to basic volumes, including any stripe sets (striped volumes) and volume sets (spanned volumes). You cannot create new striped or spanned volumes on a basic disk, but you can repair and delete these on a basic disk.

Dynamic Volumes

There are five types of dynamic volumes that can be used in Windows XP. The first three (Simple, Spanned, and Striped) can be used on any version of Windows XP. The remaining two (Mirror and RAID-5) can only be created on Windows 2000 Server, but can be managed on any version of Windows XP.

When you upgrade from basic to dynamic disk, existing partitions and logical volumes are converted into dynamic volumes. The primary partition becomes a simple volume; the system and boot partitions become system and boot volumes;

the logical drives become simple volumes; a volume set becomes a spanned volume; a stripe set becomes a stripe volume; and so on.

Volumes that have been upgraded from partitions cannot be extended. New volumes created after the conversion will be able to be extended.

NOTE: An extended volume is created when free space on a single dynamic disk is combined with an existing dynamic volume on a single drive. A spanned volume is created when two or more physical disks are used.

Simple Volume
A simple dynamic volume is the same as a volume on basic storage. It contains space from a single dynamic drive. The space combined to make a dynamic volume can be contiguous or non-contiguous space, but it MUST be on a single drive.

Spanned Volume
A spanned dynamic volume follows the same rules as volume sets on basic storage. The disk space is contained on two or more dynamic drives, up to a maximum of 32 drives. Each free space section joined in a spanned volume does not need to be approximately the same size. Spanned volumes are used to increase the size of a volume beyond the space available on one drive. The data is written to a spanned volume sequentially - that is, from beginning to end, filling up the space on one drive before moving to the next. The main drawback to spanned volumes is that if one physical drive fails, access to the data is lost on the entire spanned volume.

Striped Volume
A striped dynamic volume is similar to a stripe set on basic storage (RAID 0). There is no fault tolerance attached to a striped volume. Data is stored in equal areas of free space between 2 to 32 dynamic drives. With a striped volume, the stripe can be extended dynamically and easily, a great improvement over stripe sets on basic storage. Striped volumes are used for two reasons - to combine equal areas of free space on several physical drives into a single volume and to increase read and write performance.

I/O performance can be improved with striped volumes, because data is written and read from several disks at the same time. The disadvantage to striped volumes is that if any drive fails in the stripe, access to the data on the entire stripe is lost.

Mirror Volume
A mirror volume can only be created on Windows 2000 Server. Mirror volumes are created to make a duplicate of another volume. A prime example of this is the system and boot volumes. To create a mirror volume requires two disks.

RAID-5 Volume
A RAID-5 Volume can only be created on Windows 2000 Server. RAID-5 volumes are used much like striped volumes, except that a portion of the space is used to write parity information. This information is calculated by 1/number of disks. This portion is spaced out across all the drives so if a failure occurs, the volume can still access information by recreating it if necessary.

File Systems
Windows XP is capable of using five distinct file systems: CDFS, UDF, FAT, FAT32, and NTFS. Each of these file systems are used to store data on different types of media. First we are going to review each file system, identifying some distinct advantages and disadvantages of each.

CDFS
Windows XP provides support for CDFS, or Compact Disc File System. CDFS is compliant to ISO 9660 standards, including Level 2 standards of long file name support.
When you are creating CD-ROMs to be used on Windows XP, you must adhere to the following standards:
• All directory and file names must be less the 32 characters
• All directory and file names must be in uppercase
• The directory tree cannot exceed 8 levels from the root
• File extensions are not mandatory

NOTE: CD-ROM mastering software is not included with Windows XP.

UDF
Windows XP also provides support for UDF (Universal Disk Format), which is ISO 13346 compliant. UDF is designed for interchanging data on digital versatile disks (DVD) and CD-ROM. UDF is a cross platform solution. Windows XP reads both UDF versions 1.02 and 1.50.

NOTE: UDF mastering software is not included with Windows XP

FAT File System
FAT and FAT32 are based upon an older technology originally designed for floppy disks. It has since been expanded to its furthest limitations. FAT and FAT32 partitions are used in Windows XP to facilitate dual boot configurations.

FAT partitions have a size limitation of 2GB. In today's environment where 20GB drives are common, the limitations a FAT system imposes can be easily identified. On that 20GB drive, you would have to create 10 partitions on the drive to use all the available space.

FAT (and FAT32) both use what is known as a single cluster allocation method. Cluster sizes in FAT vary depending on the size of the partition created, and are limited to 32K. The differences in the cluster size affect the amount of wasted space that can be on the drive and the size of the partition. With the FAT file system, we have the potential for a great deal of wasted space on today's larger hard drives, as well as the numerous partitions that would need to be created.

With Windows NT 4.0, Microsoft allowed the operating system to create a FAT partition with a 64K cluster size to allow a 4GB partition to be created. The only problem is that Windows NT and Windows XP are the only operating systems that can read it.

NOTE: All file systems used by most operating systems (like Windows XP) organize your hard disk based upon cluster (or allocation unit) size. A cluster represents the smallest amount of disk space that can be allocated to hold a file.

As we see from Table 4.1, a partition of 2GB has the potential to waste a lot of space. Due to the single cluster allocation, even a 1K file gets 32K of space on the drive. This can lead to an enormous amount of unusable space on the drive. Now, back in 1990 this was not considered a very big problem.

Drives were small in comparison to today's drives. In the mid 1990's, as drive size began to radically increase, we started to experience the limitations of the FAT file system.

FAT32 File System
FAT32 was a great improvement on FAT. The most obvious of the enhancements is the ability to create partitions greater that 2GB. In fact, there is a theoretical limit of 2TB (terabytes). Although the technology is close to reaching this size most people will not have the hardware to create such a large partition! Under Windows XP we can create FAT32 partitions of up to 32GB, however it will read and write larger partitions created with other operating systems (such as Windows 98) or 3rd party tools that can create larger FAT32 partitions. The only other limitation with FAT32 is that the partition has to be greater than 32MB.

In order to be able to create larger partitions, the designers of FAT32 reworked the allocation structure of the clusters so that smaller drives (less than 8GB) only used an 8K cluster. Therefore, for that 1K file, we are now only wasting 7K, as opposed to the original 31K under FAT.

FAT32 also provides some new stability to the file system. FAT32 has the ability to relocate the root directory and use the backup copy instead of the default copy (all FAT-based file systems have 2 copies of the file allocation table).

However, FAT-based utilities, such as the MS-DOS 6.22 version of SCANDISK will corrupt the FAT32 table. This is because the program does not understand what it is trying to fix. You need to replace those tools with FAT32-aware versions.

Microsoft included FAT32 in Windows 95 OSR 2 (version 4.00.950B) and above, including Windows 98 and Windows ME. It has also added this capability to Windows XP (all versions).

NTFS File System
Microsoft realized that the FAT file system was not going to be effective in more demanding situations. FAT-based file systems did not have the reliability and security needed in those environments. When Microsoft released Windows NT 3.1, they included a new file system called NTFS (New Technology File System).

This file system broke away from the FAT file system completely. Instead of two File Allocation Tables that used single cluster allocation, it now used a single Master File Table (MFT), which works like a relational database. Where everything on the drive is an object. Another change made was the cluster allocations (Table 4.3), which were greatly improved over FAT. With this change, NTFS partitions have a theoretical limit of 16EB (exabytes), However, 2TB is the practical limit.

NOTE: Microsoft recommends only using NTFS on partitions greater than 400MB due to system overhead and performance.

The features that made NTFS stand out were built-in security, transactional logging, Unicode file names, long file name support, multiple data streams, and support for the POSIX subsystem. These features made NTFS a fast, secure, versatile, reliable, and recoverable file system.

For example, under MS-DOS using a FAT partition, if the computer shut down in the middle of writing a file, you lost the file completely. Under Windows XP using an NTFS partition, it would recover the file after the reboot. NTFS writes everything it does into a transaction log before manipulating any data on the drive. This feature is known as lazy write.

When Microsoft released Windows NT 3.51, compression was added to NTFS. This allowed files to take up even less space on the drive, freeing up some drive space. This came in very handy when storing large files that were accessed infrequently. However, with this change came a restriction - if you wanted compression, the maximum cluster size would be 4K. This is due to the compression algorithm.

Windows XP improves on NTFS again. The following is a list of new features in NTFS version 5.0:

File encryption
File encryption provides cryptographic protection of files on NTFS volumes. Encrypted File System (EFS) provides file encryption on an individual file basis using a public-key system. EFS encryption and NTFS file compression are mutually exclusive; you cannot compress an encrypted file. Sparse files may be encrypted.

Disk quotas
A disk quota allows an administrator to control the amount of data that each user can store on an NTFS volume.

Sparse files
Normally files (typically very large) containing data that is full of zeros (or a sparse data set) occupy valuable disk space. When the sparse file facilities are used, the system does not allocate hard drive space to a file except in regions where it contains something other than zeros. The default data value of a sparse file is zero.

Distributed link tracking
Distributed link tracking enables client applications to track link sources that have been moved. As a result, clients that subscribe to the link-tracking service can maintain the integrity of their references, and the objects referenced can be moved transparently.

Reparse points
These are a collection of user-defined data, which is understood by the application that stores the data. An example of this is the Microsoft Remote Storage Server (RSS) which uses reparse points when it moves infrequently used files to a long-term storage device, but maintains a pointer in the original location.

Volume mount points
This is a directory placed on an NTFS volume that provides a transparent gateway to another volume, regardless of that volume's file system. For example, you can have a mount point defined as C:\Mount\Data which is actually your D: drive.

Change log
This is a journal that records changes made to files. This is essential to recover the file system indexing used with Windows XP. This greatly reduces the amount of time it takes to reindex the whole volume in case of failures.

Which File System to Use
The file system that is recommended by Microsoft for Windows XP partitions is NTFS. It provides the security, speed, reliability, and robustness that are needed for today's notebooks, workstations, and servers.

The more drive space you wish to partition will limit your choices. FAT is effective for small partitions (512MB and less); FAT32 is effective up until 8GB; and NTFS is good for even larger partitions. However, if any security or quota management is required, NTFS is needed, no matter what size the partition is.

This does not mean that you cannot use FAT or FAT32. In fact, there are times where it is required to use one of these other file systems. Such is the case when configuring dual-boot or multi-boot systems.

when you are dual booting between Windows XP and Windows NT 4.0, it is imperative to install at least Service Pack 4 on the Windows NT 4.0 machine. Without the updates that are included, the Windows NT machine will not be able to mount and access the partition. With the update, Windows NT 4.0 can access and modify data on the Windows XP NTFS partition, as long as it does not make use of any new NTFS features (reparse points, disk quotas, encryption, sparse files, or change journal).

Deborah Timmons is a Microsoft Certified Trainer and Microsoft Certified Systems Engineer. She came into the Microsoft technical field after six years in the adaptive technology field, providing technology and training for persons with disabilities. She is the President and co-owner of Integrator Systems Inc.

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