Implementing RAID 1
on Windows Server 2003
RAID level
1 is disk mirroring. With
disk
mirroring, you use identically
sized volumes on two different
drives to create a redundant
data set. Here, the drives are
written with identical sets
of information and, if one of
the drives fails, you can still
obtain the data from the other
drive (mirror disk).
Disk mirroring
offers about the same fault
tolerance as
disk striping with
parity. Because mirrored disks
don't need to write parity information,
they can offer better write
performance in most circumstances.
However,
disk striping with
parity usually offers better
read performance because read
operations are spread out over
multiple drives.
The major
drawback to disk mirroring (RAID 1) is
that it effectively cuts the
amount of storage space in half.
For example, to mirror a 5-GB
drive, you need another 5-GB
drive. That means you use 10
GB of space to store 5 GB of
information.
Tip
If possible,
it's a good idea to mirror
boot and system volumes.
Mirroring these volumes
ensures that you'll be able
to boot the server in case
of a single drive failure.
As with
disk striping, you'll often want the
mirrored disks
to be on separate disk controllers.
This provides increased protection
against failure of the disk
controller. If one of the disk
controllers fails, the disk
on other controller is still
available. Technically, when
you use two separate disk controllers
to duplicate data, you're using
a technique known as
disk duplexing. Figure 12-5
shows the difference between
the two techniques. Where disk mirroring (RAID 1) typically uses a single
drive controller,
disk duplexing
uses two drive controllers.
If one of
the mirrored drives
in a set fails, disk
operations can continue.
Here, when users read and
write data, the data is
written to the remaining
disk. You'll need to break
the mirror before you can
fix it.
Creating a Mirror Set in Disk
Management
You create
a
mirror set by completing the
following steps:
-
In the
Disk Management Graphical
View, right-click an area
marked Unallocated on a
dynamic disk
and then choose
New Volume. This starts
the New Volume Wizard. Read
the welcome page, and then
click Next.
-
Select
Mirrored as the volume type
and create the volume.
The key difference is that
you must create two identically
sized volumes and these
volumes must be on separate
dynamic drives. You won't
be able to continue past
the Selected Disks window
until you've selected the
two disks that you want
to work with.
-
As with
other
RAID techniques,
mirroring
is transparent to users.
Users see the mirrored set
as a single drive that they
can access and use like
any other drive.
More Info
The
status of a normal
mirror
is Healthy. During the
creation of a mirror,
you'll see a status
of Resynching. This
tells you that Disk
Management is creating
the mirror.
Mirroring an Existing Volume
Rather than
creating a new mirrored volume,
you can use an existing volume
to create a
mirrored set. To
do this, the volume you want
to mirror must be a simple volume
and you must have an area of
unallocated space on a second
dynamic drive of equal or larger
space than the existing volume.
In Disk Management,
you mirror an existing volume
by completing the following
steps:
-
Right-click
the simple volume you want
to mirror and then select
Add Mirror. This displays
the Add Mirror dialog box.
-
Use the
Disks list box to select
a location for the mirror
and then click Add Mirror.
Windows Server 2003 begins
the mirror creation process
and you'll see a status
of Resynching on both volumes,
as shown in Figure 12-6.
This page is about:
disk mirroring,
raid 1,
implementing disk mirroring,
implementing raid 1,
implementing raid 1 on windows server 2003,
implementing disk mirroring on windows server 2003,
mirrored set,
mirror set,
mirrored volume,
mirror disk
disk duplexing
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