Basic Disks

 

In Windows 7, basic disks are by far the most oftenly used.. The “basic disk” term refers to a disk that contains one or more partitions, such as primary partitions or logical drives, which are usually formatted with a particular file system to become a volume that can be used for file storage. Basic disks can provide a simple storage solution that accommodates a useful array of changing storage requirement scenarios. Basic disks also support other clustered disks and even universal serial bus removable drives. In order for them to be backward compatibility, basic disks usually use the same Master Boot Record partition style as the disks used by the MS-DOS operating system and all previous versions of Windows but can also support GUID Partition Table (GPT) partitions on systems that support it. (msdn.microsoft.com)

It is possible to add more space to already existing primary partitions and logical drives by extending them into adjacent, unallocated and contiguous space on the same diskdrive . In order to extend a basic volume, the only requirement is that it is formatted using the NTFS file system. It is also possible to extend a logical drive within the contiguous free space in the extended partition that contains that logical drive. If you wish to extend a logical drive beyond the available free space in the extended partition, the extended partition increases its size in order to contain this logical drive.

The operations that can be performed only on basic disks are: to create or delete primary and extended partitions; to create and delete logical drives within an extended partition; and to format a partition.

Dynamic Disks

 

Dynamic disks provide advanced and important features that basic disks can not provide, like the ability to create volumes that span multiple disks (striped and spanned volumes) and the ability to create fault-tolerant volumes (mirrored or RAID-5 volumes). Dynamic disks can use the MBR or GPT partition styles on systems that support both. The volumes on dynamic disks are also known as dynamic volumes. Dynamic disks offer users much greater flexibility when it comes to volume management because they use a database to track the information about dynamic volumes on the disk and if applicable the other dynamic disks in use on the same computer. Each dynamic disk stores a replica of the dynamic disk database, therefore a corrupted dynamic disk database is able to repair one dynamic disk by using the database on another dynamic disk. The partition style of the disk determines the location of the database:

• On MBR partitions, the database is contained in the last 1 megabyte (MB) of the disk.
• On GPT partitions, the database is contained in a 1-MB reserved (hidden) partition.

Dynamic disks can also be viewed as a separate type of volume management that allows volumes to have noncontiguous extents on one or more physical disks. Dynamic disks and volumes rely on features like the Logical Disk Manager (LDM) or the Virtual Disk Service (VDS). These features enable the user to perform tasks such as converting dynamic disks from basic disks, and creating fault-tolerant volumes. In order to encourage the use of dynamic disks, Microsoft decided to remove multi-partition volume support for basic disks. (technet.microsoft.com)

The operations that can be performed on dynamic disks are: to create and delete simple, spanned, striped, mirrored, and RAID-5 volumes; to extend a spanned or simple volume, to remove a mirror from a mirrored volume or break the mirrored volume into two or more volumes and to repair mirrored and RAID-5 volumes.

An important difference between dynamic and basic disks is that dynamic disk volumes can be created from a set of noncontiguous extents on one or multiple physical disks while a volume on a basic disk consists of one set of contiguous extents on one disk. Because of the size of the disk space needed for the LDM database, Windows 7 will not be able to convert a basic disk to a dynamic disk unless there is at least 1 MB of free space on the disk.

Independently of a dynamic disk using a MBR or GPT partition style, users are able to create up to 2,000 dynamic volumes, but Microsoft recommends that the  number of dynamic volumes should be a maximum of 32.

Portable Computers

Unfortunately, the option to convert a basic disk to a dynamic disk is not available on portable computers. This happen because the Windows Disk Management console does not allow this upgrade on a portable device. Most of the times, portable computers support a single internal disk.  Therefore, they cannot benefit from the advanced options that dynamic disks provide. Dynamic disks have advantages compared to basic disks only when there are at least two dynamic disks.

Types of Dynamic Volumes

 

A dynamic volume is a volume created on a dynamic disk. Dynamic volume can be: simple, spanned, and striped. Windows 7 also supports mirrored and RAID-5 volumes, which are fault tolerant, meaning that the computer hardware or software is still available, even if there is an unexpected hardware failure.

Whether the partition uses a MBR or GPT style, users are able to create 1000 dynamic volumes per disk group, but the drawback is that boot time increases considerably. Microsoft recommends that the number of dynamic volumes does not exceed 32 for each disk group.

Simple Volumes

Simple volumes on dynamic disks are the equivalent of the primary partitions and logical drives discussed earlier in basic disks. When creating simple volumes it is important for users to remember that if there is only one dynamic disk, only one simple volume can be created. The size can be increased to include unallocated space on the same disk or on a different disk. The volume must be either unformatted or formatted using NTFS. There are two ways to increase the size of a simple volume in two ways: by extending the simple volume on the same disk, or by extending a simple volume to include unallocated space on other disks on the same computer. It is important to remember that in case the simple volume is the system volume or the boot volume, it can not be extended. (technet.microsoft.com)

Spanned Volumes

Spanned volumes are created by combining areas of unallocated space from multiple disks into one logical volume. The areas of unallocated space can have various sizes. Spanned volumes require two disks, but users can use up to 32 disks. When creating spanned volumes, it is important to remember that only NTFS volumes or unformatted volumes can be extended.

After a spanned volume is created or extended it is impossible to delete any portion of it without deleting the entire spanned volume. Spanned volumes can not be striped or mirrored.

Unlike some may believe, spanned volumes do not provide any fault tolerance. It is enough for one of the disks containing a spanned volume to fail, and the entire volume fails, and all data on the spanned volume will become unusable. The reliability for a whole spanned volume can be seen as the reliability of the the least reliable disk in the set.

The most important usage of a spanned volume is to create a spanned volume in order to increase volume size. Spanned volumes are oftenly created by users who have two or more disks. If the user doesn’t require the high read throughput of a striped volume or the fault tolerance offered by mirrored or RAID-5 volumes, the user will most likely create a spanned volume.

If the data on a user’s primary disk does not fit, the user can extend that volume onto a second disk in the same computer. This enables the user to create a big volume that uses space on two disks. The volume can be extended to cover as much as 32 disks.

Striped Volumes

Striped volumes are important because they can improve disk performance by distributing input or output requests at the same time across multiple disks. Striped volumes are composed of stripes of data of equal size that are written across each disk in the same volume. They are created from equally sized, unallocated areas on at least two disks. In Windows 7, the Microsoft suggested size of each stripe is 64 kilobytes (KB).

Obviously, striped volumes cannot be extended or mirrored and do not offer any fault tolerance. If one of the disks containing a striped volume fails, the entire volume fails, and all data on the striped volume is lost.

Striped volumes are typically created by users who have at least two disks in their computers and require high read and write throughput but do not require fault-tolerance.

Mirrored Volumes

A mirrored volume is a fault-tolerant volume that provides an exact copy of a volume on another disk on the same computer. In other words, mirrored volumes provide data redundancy by duplicating the information contained on the volume. The two disks that make up a mirrored volume are also known as mirrors. In case one of the disks fails, the data on the failed disk, obviously, becomes unavailable, but the system continues to operate by using the properly working disk.

Users should create a mirrored volume whenever they need to protect critical data. Mirrored volumes are typically created by the user who requires fault-tolerance and who has at least two disks in their computer. Mirrored volumes provide better write performance than RAID-5 volumes. (technet.microsoft.com)

Users can also use the mirroring process to migrate data to a larger disk. If you run out of room on the simple you can move this data to a larger disk instead of creating a spanned volume. A  mirrored volume can be created using the simple volume containing the data and a larger disk. After creating the mirrored volume, the mirrored volume can be broken and extended, leaving a complete copy of the original volume with available space for new data. The space on the original volume can be reclaimed for other uses.

RAID-5 Volumes

A RAID-5 volume is a fault-tolerant volume that stripes data and parity across three or more disks. Parity is a calculated value that is used to reconstruct data if one disk fails. When a disk fails, Windows 7 continues to operate by recreating the data that was on the failed disk from the remaining data and from the parity disk. Users should create a RAID-5 volume in order to protect critical data.

 

Upgrading basic disks to dynamic disks

 

To upgrade a basic disk to a dynamic disk, users have to follow the steps below:

1. In Disk Management, right-click a basic disk that you want to upgrade, either in the Disk List view or in the left pane of the Graphical view. Then select Upgrade To Dynamic Disk.
2. In the Upgrade To Dynamic Disk dialog box, select the check boxes for the disks you want to upgrade. If you’re upgrading a spanned, striped, mirrored, or RAID-5 volume, be sure to select all the basic disks in this set. You must upgrade the set together.
3. The Disks To Upgrade dialog box shows the disks you’re upgrading. The buttons and columns on this dialog box contain the following information:
   • Name Shows the disk name or number.
   • Disk Contents Shows the type and status of partitions, such as boot, active, or in use.
   • Will Upgrade Specifies whether the drive will be upgraded. If the drive doesn’t meet the criteria, it won’t be upgraded, and you may need to take corrective action, as described previously.
   • Details Shows the volumes for the selected drive.
   • Upgrade button Starts the upgrade operation.