6. Managing volumes on dynamic disks
Any disk using the MBR or GPT partition style can be configured as a
dynamic disk. Unlike basic disks, which have basic volumes that can be
created as primary partitions, extended partitions, and logical drives,
dynamic disks have dynamic volumes that can be created as the following
types:
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Simple volumes
A simple volume is a volume that’s on a single drive and has the same purpose as a primary partition.
-
Spanned volumes
A spanned volume is a volume that spans multiple drives.
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Striped volumes
A striped volume is a volume that uses RAID 0 to combine multiple disks into a striped set.
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Mirrored volumes
A mirrored volume
is a volume that uses RAID 1 to mirror a primary disk onto a secondary
disk that is available for disaster recovery.
-
RAID-5 volumes
A RAID-5 volume is a volume that uses RAID 5 to create a fault-tolerant striped set on three or more disks.
Techniques for creating and managing
these volume types are discussed in the sections that follow. Keep in
mind that the RAID technology built into the operating system is
software-based and is being phased out. Standards-based storage also has software RAID options, and they’re preferred for new server deployments.
6.1 Creating a simple or spanned volume
You create simple and spanned volumes in much the same way. The differences between these volume types are subtle:
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A simple volume uses free space from a single disk to create a
volume. Windows is able to write to the selected disk until there is no
more free space available within the volume.
-
A spanned volume is used to combine the disk space on multiple disks
to create the appearance of a single volume. Windows always writes to
the first disk in the spanned set first and then when this disk fills,
Windows writes to the second disk, and so on.
If you later need more space, you can extend a simple or spanned
volume type by using Disk Management. Here, you select an area of free
space on any available disk and add it to the volume. When you extend a
simple volume onto other disks, it becomes a spanned volume. Any volume
that you want to extend should be formatted using NTFS because only NTFS
volumes can be extended.
Simple and spanned volumes aren’t fault tolerant. If you create a
volume that spans disks and one of those disks fails, you won’t be able
to access the volume. Any data on the volume will be lost. You must
restore the data from backup after you replace the failed drive and
re-create the volume.
To create a simple or spanned volume, complete the following steps:
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In Disk Management Graphical View, press and hold or right-click an
area marked Unallocated on a dynamic disk, and then choose New Simple
Volume or New Spanned Volume as appropriate. Read the Welcome page and
then tap or click Next.
-
If you select New Spanned Volume, you next see the Select Disks page shown in Figure 26.
Use this page to select disks that should be part of the volume and to
size the volume segments on the designated disks. Select one or more
disks from the list of disks that are available and have unallocated
space. Tap or click Add to add the disk or disks to the Selected list
box. Next, select each of the disks in turn, and then specify the amount
of space you want to use on the selected disk. Tap or click Next when
you are ready to continue.
Note
If you started with a dynamic disk, the disk wizard shows both basic
and dynamic disks with available disk space. If you add space from a
basic disk that is not a system or boot volume, the wizard will attempt
to convert the disk to a dynamic disk before creating
the volume set. Before tapping or clicking Yes to continue, make sure
you really want to do this because this can affect how the disk is used
by the operating system.
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Use the Assign Drive Letter Or Path page to assign a drive letter or
path. You can also choose Do Not Assign A Drive Letter Or Drive Path if
you want to create the partition without assigning a drive letter or path. Tap or click Next.
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Use the Format Volume page, to set the formatting options. Simple and spanned volumes
can be formatted by using FAT, FAT32, exFAT, NTFS, or ReFS. If you
think you might need to extend the volume at a later date, you might
want to use NTFS because NTFS can be easily extended.
-
Tap or click Next. The final page shows you the options you selected.
If the options are correct, tap or click Finish. The wizard then
creates the volume and configures it.
6.2 Configuring RAID 0: Striping
RAID level 0 is disk striping. With disk striping, two or more volumes—each
on a separate drive—are configured as a striped set. Unlike spanning,
Windows breaks the data to be written into blocks called stripes
and then writes the stripes sequentially to all disks in the set. So,
if there are three disks in the set, Windows writes part of the data to
the first disk, part of the data to the second disk, and part of the
data to the third disk—this process of alternating between the disks is
called striping.
Although the boot and system volumes shouldn’t be part of a striped
set, you can place volumes for a striped set on up to 32 drives, but in
most circumstances sets with 2 to 5 volumes offer the best performance
improvements. When 3 to 32 drives are used, the major advantage of disk
striping is speed. Data can be accessed on multiple disks using multiple
drive heads, which improves performance considerably. When you try to
use more than 32 drives, the performance improvement decreases
significantly.
When you create striped sets, you’ll want to use volumes that are
approximately the same size. Disk Management bases the overall size of
the striped set on the smallest volume size. Specifically, the maximum
size of the striped set is a multiple of the smallest volume size. For
example, if the smallest volume is 100 GBs, the maximum size for a
three-disk striped set is 300 GBs.
You can maximize performance using disks that are on separate disk
controllers. This allows the system to simultaneously access the drives.
Keep in mind that this configuration offers no fault tolerance. If any
hard disk drive in the striped set fails, the striped set can no longer
be used, which essentially means that all data in the striped set is
lost. You’ll need to re-create the striped set and restore the data from
backups.
You can create a striped set by following these steps:
-
In the Disk Management Graphical View, press and hold or right-click
an area marked Unallocated on a dynamic disk and then choose New Striped
Volume. This starts the New Striped Volume Wizard. Read the Welcome
page, and then tap or click Next.
-
Create the volume . The key difference is that you need at least two dynamic disks to create a striped volume.
After you create a striped volume, you can use the volume just like
any other volume. You can’t extend a striped set after it’s created.
Therefore, you should carefully consider the setup before you implement
it.
6.3 Recovering a failed simple, spanned, or striped disk
Simple disks are the easiest to troubleshoot and recover because
there is only one disk involved. Spanned or striped disks, on the other
hand, have multiple disks and the failure of any one disk makes the
entire volume unusable. The drive status might show as Missing, Failed,
Online (Errors), Offline, or Unreadable.
The Missing (and sometimes Offline) status usually happens if drives
have been disconnected or powered off. If the drives are part of an
external storage
device, check the storage device to ensure that it is connected properly
and has power. Reconnecting the storage device or turning on the power
should make it so that the drives can be accessed. You then must start
Disk Management and rescan the disks by selecting Rescan Disks from the
Action menu. When Disk Management finishes, press and hold or
right-click the drive that was missing, and then choose Reactivate.
The Failed, Online (Errors), and Unreadable statuses indicate
input/output (I/O) problems with the drive. As before, try rescanning
the drive, and then try to reactivate the drive. If the drive doesn’t
come back to the Healthy state, you might need to replace it.
One of the advantages that dynamic disks have over basic disks is
that you can easily move them from one computer to another. For example,
if after setting up a server, you decide that you don’t really need its
two additional hard disk drives, you could move them to another server
where they could be better used. Before you move disks, you should
access Disk Management on the server where the dynamic disks are
currently installed and check their status. The status should be
Healthy. If it isn’t, you should fix any problems before moving the
disks.
Next check to see whether any dynamic
disks that you want to move are part of a spanned, extended, mirrored,
striped, or RAID-5 set. If they are, you should make a note of which
disks are part of which set and plan on moving all disks in a set
together. If you are moving only part of a disk set, you should be aware
of the consequences. For spanned, extended, or striped volumes,
moving only part of the set will make the related volumes unusable on
the current computer and on the computer to which you are planning to
move the disks. If you plan to move only one disk of a mirrored volume,
you should break the mirror before you move it. This ensures that you
can keep using the disks on both computers. For RAID-5 volumes, you
should move all of the disks in the set if possible. If you move only
part of the RAID-5 set, you might find that you can’t use the set on
either computer.
To move the disks, open Computer Management and then, in the left
pane, select Device Manager. In the Device List, expand Disk Drives.
This shows a list of all the physical disk drives on the computer. Press
and hold or right-click each disk that you want to move, and then
select Uninstall. If you are unsure which disks to uninstall, press and
hold or right-click each disk and select Properties. In the Properties
dialog box, click the Volumes tab and then choose Populate. This shows
you the volumes on the selected disk. In Computer Management, select
Disk Management. Press and hold or right-click each disk that you want
to move, and then select Remove Disk.
After you perform these procedures, you can move the dynamic disks.
If the disks are hot swappable and this feature is supported on both
computers, remove the disks from the original computer and then install
them on the destination computer. Otherwise, turn off both computers,
remove the drives from the original computer, and then install them on
the destination computer. When you’re finished, restart the computers.
On the destination computer, access Disk Management, and then select
Rescan Disks on the Action menu. When Disk Management finishes scanning
the disks, press and hold or right-click any disk marked Foreign and tap
or click Import. You should now be able to access the disks and their volumes on the destination computer.
Note
When you move dynamic
disks, the volumes on those disks should retain the drive letters they
had on the previous computer. If a drive letter is already used on the
destination computer, a volume receives the next available drive letter.
If a dynamic volume previously did not have a drive letter, it does not
receive a drive letter when moved to another computer. Additionally, if
automounting is disabled, the volumes aren’t automatically mounted and
you must manually mount volumes and assign drive letters.