Dell OpenManage Array Manager 2.5 User's Guide
Basic and Dynamic Disk Overview
This chapter describes conceptual and procedural information about how Array Manager implements basic and dynamic disks. It also includes general disk functions. The main topics in this chapter are:
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Note: This section does not apply to NetWare® servers. |
Physical disks can be either basic or a new type called dynamic. When you install the Microsoft® Windows NT® 4.0 or Windows 2000® operating system, your hard disks are automatically initialized as basic. You can upgrade them to dynamic after the Array Manager installation is complete.
Basic disks use the traditional disk partitioning mechanism used by MS-DOS®, Microsoft® Windows 95® or 98®, and Microsoft Windows NT operating systems. A basic disk can have up to either four primary partitions or three primary partitions plus an extended partition. This extended partition can be subdivided into a number of logical drives.
In Array Manager, a basic disk can also have "legacy" partitions and volumes if the disk was previously configured with Microsoft Windows NT Disk Administrator. These "legacy" volumes are different from volumes that you create with Array Manager. Array Manager does not allow you to change Disk Administrator volumes, but it lets you view and do limited management of them. See Manage Volumes Created with Windows NT Disk Administrator in the Volume Management chapter for more information.
You can create only primary and extended partitions on basic disks. You should create partitions on basic disks if you want computers running Microsoft Windows 98 or earlier, or MS-DOS to access these partitions.
A dynamic disk is a physical disk that can contain dynamic volumes created with Volume Manager. A dynamic volume organizes space on one or more physical disks by using a specific type of volume layout. The five types of dynamic volumes are simple, spanned, mirrored, striped, and RAID-5.
On a dynamic disk, space is organized through volumes rather than partitions. Because a dynamic disk does not have the partitioning scheme used by Windows 95/98 and MS-DOS, you cannot access dynamic disks through those operating systems.
For more information on the dynamic volume types, see the Dynamic Volume Types in the Volume Management chapter.
This section's topics are:
Array Manager allows you to do the following on basic disks:
You cannot perform the following tasks on a basic disk:
Use the Create Volume wizard to create primary partitions and extended partitions on a basic disk.
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Note: If the disk already has either four primary partitions or three primary partitions and one extended partition, Array Manager displays a message that you have exceeded the number of partitions and will not let you create any more. Click OK and return to the Array Manager console. |
An extended partition can be subdivided into as many as 32 logical drives. You can use all or part of the free space in an extended partition when creating logical drives. An extended partition or a logical drive cannot span multiple disks.
In the graphical view, removable-media devices are labeled Removable. They are considered basic disks.
You can create only one primary partition on removable-media devices. You cannot create extended partitions, logical drives, or dynamic volumes on removable-media devices. You cannot upgrade removable-media devices to dynamic volumes. Removable-media devices can contain only one primary partition and can be formatted with FAT or NTFS. You cannot mark a primary partition on a removable-media device as active.
On Windows NT, a basic disk can be upgraded to dynamic only if it does not contain partitions, logical drives, or basic volumes.
On Windows 2000, Array Manager can upgrade a basic disk that contains partitions, logical drives, or Disk Administrator volumes. Array Manager converts the partitions and logical drives to simple dynamic volumes and the Disk Administrator volumes to dynamic volumes of the appropriate corresponding RAID type. This capability is called encapsulation and is described in more detail in Upgrade Disks with Legacy Volumes to Dynamic in the next chapter, Volume Management.
After you upgrade a basic disk to a dynamic disk, you cannot change the dynamic volumes back to partitions or basic volumes. A dynamic disk cannot contain partitions or logical drives, nor can it be accessed by the MS-DOS or Windows 95/98 operating systems.
This section's topics are:
When you upgrade a dynamic disk, Array Manager writes a small database onto the upgraded disk to store volume management information about the disk and all other dynamic disks present on your system. This database is what gives a dynamic disk many advantages:
Dynamic disks cannot be accessed by MS-DOS or Microsoft Windows 95/98. The Microsoft Windows NT and Windows 2000 operating systems can access dynamic disks, but the dynamic volumes on dynamic disks cannot be changed without Array Manager.
You can create dynamic volumes on dynamic disks only. To create and delete simple, spanned, striped, mirrored, and RAID-5 volumes, see Creating a Dynamic Volume in the Volume Management chapter.
You can extend simple and spanned volumes without having to locate unallocated contiguous space on the disk. See Extending a Dynamic Simple or Spanned Volume in the Volume Management chapter.
A dynamic disk may appear as a missing disk when it is corrupted, powered down, or disconnected. You can reactivate a dynamic disk to bring it back online.
Dynamic disks with a Foreign status are disks that have been moved from another computer. You cannot reactivate a foreign disk. To change a foreign disk's status and enable it to be seen as a part of the current computer system, you will need to use the command Merge Foreign Disk. For details on how this command is done, see the next topic Moving a Dynamic Disk to Another Computer.
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Note: It is recommended that you back up all data on your volumes before you move disks to another computer. |
Before you disconnect the disks, make sure the status of the volumes on the disks is Healthy. If the status is not Healthy, you should repair the volumes before you move the disks. You need to prepare disks for removal in some cases. See Prepare to Remove in the Configuring PERC 2/SC, 2/DC, 3/DCL RAID Controllers chapter.
You can revert a dynamic disk to basic if there are no volumes on the disk. If volumes exist, you must delete them before you can revert the disk. Disks shown in Array Manager to be unreadable or to be Foreign disks can be reverted, but doing so causes you to lose all existing data on the reverted disk.
This section on general disk functions has the following topics:
Array Manager should detect the new disk after you click Rescan. However, if Array Manager does not detect the new disk, you may need to restart your computer.
New disks are added to the computer as basic disks. On Windows NT 4.0, you can upgrade a new disk to dynamic as long as the basic disk is empty. It cannot contain volumes or partitions. On Windows 2000, you can update basic disks that contain data to dynamic. See the section Upgrade Disks with Legacy Volumes to Dynamic in the Volume Management chapter.
When Array Manager rescans disks, it scans all attached disks for disk configuration changes. It also updates information on removable media, CD-ROM drives, basic volumes, file systems, and drive letters.
Every time you remove or add disks to a computer, you must click Rescan and then verify that the disk information is correct.
From the View pull-down menu, select Rescan, or select the Rescan icon from the toolbar.
A rescan can take several minutes, depending on the number of devices installed.
Use this option to refresh drive letter, file system, volume, and removable-media information. Refresh also checks to see whether unreadable volumes are now readable. However, it does not scan hardware. To update hardware information, use Rescan instead.
For PERC, 2/SC, and 2/DC controllers, a disk must have a signature on it before it can be used. If you have a PERC 2, 2/Si, 3/Si, or 3/Di controller, this task is not necessary.
When you create a virtual disk and then do a rescan, the newly created virtual disk appears under the Disks node. The disk will display an error bitmap on the icon. The Disk Type is Unsigned Disk. If left unsigned, the disk cannot be used.
Right-click on the unsigned disk. The Write Signature command appears on the context menu that comes up. (The Write Signature command appears only if a disk does not have a signature on it.) Select this command to write a signature on the disk.
Once a signature is written on a disk, the disk will display as a Basic Disk. You can create partitions on the basic disk, or you can upgrade the disk to dynamic to create volumes on it.
Array Manager supports Self Monitoring Analysis and Reporting Technology (S.M.A.R.T.) on array disks that are S.M.A.R.T. enabled.
S.M.A.R.T. performs predictive failure analysis on each disk and sends alerts if a disk failure is predicted. The RAID controllers check array disks for failure predictions and, if found, pass this information to the Array Manager console. Array Manager immediately displays an alert icon on the disk. Array Manager also raises an alert under the Events tab and in the Windows NT/2000 Event Log.
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Note: When a controller's I/O is paused, you will not receive S.M.A.R.T. events. |