RAID Utility
User’s Guide
Instructions for setting up RAID volumes
on a computer with a MacPro RAID Card
or Xserve RAID Card.
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Contents
RAID Utility User’s Guide
Installing the RAID Software
Running RAID Utility
Setting Up RAID Volumes
Migrating an Existing Volume to a RAID Volume
Creating a RAID Set
Creating a Volume
Setting Up a Spare Drive
Reverting a Spare Drive
Deleting a Volume or RAID Set
Solving Problems
Using the Command Line
About RAID Levels
Using Non-RAID JBOD Disks
Setup Examples
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RAID Utility User’s Guide
This guide shows you how to set up RAID volumes using the
RAID Utility application on a computer with a Mac Pro RAID
Card or Xserve RAID Card.
With a Mac Pro RAID Card or Xserve RAID Card installed in your computer, you can use
RAID Utility to turn your computer’s internal disks into storage volumes based on RAID
(redundant array of independent disks) schemes that improve performance and
protect your data.
Installing the RAID Software
If you purchased your computer with a RAID card installed, the RAID software is already
installed on your startup disk and RAID Utility is in /Applications/Utilities/. RAID Utility
is also available from the Utilities menu when you start up your computer using the
Mac OS X installation disc that comes with the computer.
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Running RAID Utility
The RAID Utility application is in /Applications/Utilities/. You can open it from there
anytime you want to check the status of the RAID components in your computer.
You can also run RAID Utility from the Installer when you start up your computer using
the Mac OS X or Mac OS X Server installation disc that comes with the computer.
Choose Utilities > RAID Utility while you are in the Installer.
Note: If you plan to perform any setup tasks that affect the computer’s startup disk (for
example, migrating the startup disk or otherwise reusing the startup disk to create new
RAID sets or volumes), you need to start up the computer from the installation disc that
comes with your computer or from an external disk on which you have installed
Mac OS X or Mac OS X Server using that installation disc.
The RAID Utility Window
Show or hide
the toolbar
Overall RAID status
Items belonging
to the selected
component
Components of your
RAID configuration
RAID battery status
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Setting Up RAID Volumes
There are two basic ways to set up RAID volumes:
 Migrate an existing startup volume
 Set up RAID sets and volumes manually
For examples of some typical setups, see “Setup Examples” on page 17.
Migrating an Existing Startup Volume
The simplest way to set up RAID volumes on a new computer is to use the Migrate
RAID Set command to convert the existing startup volume, together with other empty
disks in the computer, to one or two RAID volumes in a single step. When you migrate
your existing startup volume, you don’t need to reinstall the operating system.
Note: You can only migrate a volume that is based on an Enhanced JBOD RAID set.
When you purchase a computer with the RAID card installed, the startup volume is set
up this way.
To migrate your disks to one or two RAID volumes:
m Follow the instructions under “Migrating an Existing Volume to a RAID Volume” on
page 6.
Setting Up RAID Sets and Volumes Manually
If you want to create more than two volumes or want more control over RAID set and
volume setup, and you don’t mind reinstalling Mac OS X or Mac OS X Server, you can
use the Create RAID Set and Create Volume commands to set up your RAID storage.
To set up RAID sets and volumes manually:
1 Start up the computer using the Mac OS X or Mac OS X Server installation disc that
comes with the computer
2 When the Installer opens, choose your language and click the Next button to see the
Utilities menu in the menu bar at the top of the screen.
3 Choose Utilities > RAID Utility.
4 In RAID Utility, use the Create RAID Set and Create Volume commands to create your
RAID volumes.
For information, see “Creating a RAID Set” on page 8, and “Creating a Volume” on
page 9.
5 When you have created your volumes, quit RAID Utility.
6 Follow the Installer onscreen instructions to install Mac OS X or Mac OS X Server on one
of the new RAID volumes and restart the computer.
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Migrating an Existing Volume to a RAID Volume
When you purchase a computer with the RAID card installed, the startup disk is
configured as a single-disk Enhanced JBOD RAID set. You can convert this RAID set,
along with one, two, or three empty disks, to a RAID volume in one step using the
Migrate RAID Set command. All files on the single original disk are moved to the new
RAID volume. Files on the additional disks are erased.
To migrate to a RAID volume:
1 Start up your computer using the Mac OS X or Mac OS X Server installation disc that
comes with the computer.
2 When the Installer opens, choose your language and click the Next button to see the
Utilities menu at the top of the screen.
3 Choose Utilities > RAID Utility.
4 Select the existing RAID set, which supports your current startup volume, in the left
column of the RAID Utility window.
5 Click Migrate RAID Set in the toolbar.
6 Choose the type of RAID volume you want to create.
Maximum Protection: Migrates your system to a RAID volume based on either the
RAID 1 or RAID 5 level, depending on the number of drives available.
Maximum Performance: Creates a volume based on the RAID 0 level.
7 Choose the additional drives you want to include in the volume.
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8 Under Options, choose whether you want to use space from the additional drives to
create a second volume or leave the extra space free for creating other volumes later.
Create new volume using added capacity: Creates a RAID-based duplicate of the original
startup volume and a second RAID volume with all the remaining space available on
the underlying RAID set. You get two volumes in the Finder—a startup volume and an
empty data volume.
If you don’t select this option, RAID Utility creates a single RAID-based duplicate of the
original startup volume and leaves the remaining space on the RAID set free for you to
use to create other volumes when you want.
9 Click Migrate.
10 When the migration process is finished, quit RAID Utility.
11 Quit the Installer and restart the computer.
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Creating a RAID Set
Before you can create a RAID volume, you need to combine physical drives into a
logical disk called a RAID set.
The number of drives needed to create a RAID set depends on the RAID level you want
to use. You can use a single drive to create an Enhanced JBOD set, two drives to create
a RAID 0 or RAID 1 set, three or four drives to create a RAID 0 or RAID 5 set, or four
drives to create a RAID 0+1 set.
To create a RAID set:
1 Open RAID Utility and click Create RAID Set.
2 In the dialog that appears, choose the RAID level you want to use.
The RAID levels you can select depend on the number of drives you choose. If the RAID
level you want to use is not enabled, try selecting additional drives.
3 Select the drives you want to include in the set.
4 Select the options that you want to apply to the set.
Use unassigned drives as spares: Reserves any drive not selected for the RAID set as a
spare that will be used if a drive in the set fails. You can’t assign a spare to a RAID 0 or
Enhanced JBOD set.
5 Click Create.
For information about RAID levels, see “About RAID Levels” on page 15.
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Creating a Volume
To create a RAID volume, you use RAID Utility to format space available on a RAID set.
To create a volume:
1 In RAID Utility, select a RAID set in the left column and click Create Volume.
2 Type a name for the volume.
3 Choose a volume format from the pop-up menu.
If you’re not sure which format to use, choose Mac OS X Extended (Journaled).
4 Enter a size for the volume.
This is initially set to the size of the underlying RAID set, but you can enter a smaller
size and save the remaining space to create other volumes.
5 Click Create Volume.
You can start using the volume as soon as its icon appears in the Finder, but maximum
read and write performance isn’t available until the volume is completely initialized.
Until then, the volume status icon in RAID Utility is yellow. Initialization time depends
on the RAID level of the underlying RAID set. To check progress, click Tasks in the left
column of the RAID Utility window.
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Setting Up a Spare Drive
You can set aside an unassigned drive as a global spare. Then, if any disk in a RAID set
fails, the spare is automatically integrated into the set to take the place of the failed
disk. Only RAID 1, RAID 0+1, and RAID 5 sets can take advantage of spare drives.
To set up a spare drive:
1 Open RAID Utility.
2 Select the drive you want to use as a spare in the left column.
3 Choose RAID > Make Spare.
You can also assign unused drives as spares by selecting the “Use unassigned drives as
spares” option when you create a set using the Create RAID Set command.
Reverting a Spare Drive
You can use the Revert Spare command to return a spare drive to general availability so
you can use the drive to create RAID sets.
To revert a spare drive:
1 Open RAID Utility.
2 Select the drive in the left column.
3 Choose RAID > Revert Spare.
Deleting a Volume or RAID Set
As a first step in modifying your RAID configuration, you can delete an existing volume
or RAID set to free up the drives needed to create a new volume or RAID set.
Note: To delete the computer’s startup volume or the RAID set that the startup volume
is based on, you must first start up the computer from a different disk that has the RAID
software installed, such as
 the Mac OS X or Mac OS X Server installation disc that comes with your computer
 an external disk on which you have installed Mac OS X or Mac OS X Server using the
installation disc that comes with your computer
Important: When you delete a RAID set, all volumes based on that RAID set are also
deleted.
To delete a RAID set or a volume:
1 Open RAID Utility and choose the volume or RAID set in the left column.
2 Click Delete Volume or Delete RAID Set.
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Solving Problems
The following paragraphs may help you identify or solve a problem you’re having with
your RAID volumes.
Checking the Status of RAID Components
You can use RAID Utility to check the status of the RAID card, its battery, your RAID
volumes, and the disk drives and RAID sets they are built on.
Overall status
Click to clear event
List of events
To check the status of a component:
1 Open RAID Utility.
2 Click an item in the component list on the left side of the window.
You can also check RAID component status using System Profiler. Choose About This
Mac from the Apple menu and click More Info. Then select Hardware RAID under
Hardware in the Contents list. System Profiler is also available in /Applications/Utilities/.
Self-Monitoring, Analysis, and Reporting Technology (SMART) status information for
disks is available only for SATA drives.
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Reviewing Event Messages
RAID Utility keeps a list of events related to the current state of the RAID card, RAID
volumes, and their components.
To view events:
1 Open RAID Utility.
2 Click Status, under Controller, in the list on the left side of the window.
To erase an event, click the button in the Clear column.
Verifying a RAID Set
You can use the Verify RAID Set command to confirm that data stored on a RAID 1,
RAID 0+1, or RAID 5 volume is protected.
The performance of the RAID set and any volume based on it is degraded during
verification.
To verify a RAID set:
1 Open RAID Utility.
2 Select the RAID set in the list on the left side of the window.
3 Click Verify RAID Set.
If the verification process reports problems, you can use the command
$ raidutil modify volume --rewrite
in Terminal to recreate the volume’s data protection information. For information, see
the raidutil man page or type raidutil at the command-line prompt.
If Write Caches are Disabled
The RAID card backup battery may not be fully charged. To protect your data, the RAID
card automatically disables write caching whenever the battery is not fully charged.
Once every three months the RAID card reconditions the battery by completely
discharging and then recharging it.
If the Battery is Not Fully Charged
Every three months, the RAID card automatically reconditions its battery by completely
discharging and then recharging it. During the reconditioning cycle, you may see an
alert advising you that the 72-hour battery reserve is unavailable and the controller
status may indicate that write caches are disabled. Performance may be slightly
degraded during this time, but will return to normal when the battery is recharged.
To check battery status:
1 Open RAID Utility.
2 Click Status in the left column.
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The current state of the battery is also indicated by the icon in the lower-left corner of
the RAID Utility window.
If a Volume is Degraded
A degraded volume is either not providing full performance or has lost its ability to
guarantee data protection. All data on a degraded volume is available, but data will be
lost if a disk fails. A volume’s status is listed as degraded:
 While the volume is being created. This is normal, and the volume’s status changes
from degraded to good as soon as initialization is finished.
 When a disk fails in the RAID 1, RAID 5, or RAID 0+1 set that the volume is based on.
The volume remains in a degraded state until you replace the faulty drive or until an
available spare is integrated into the RAID set.
 While the RAID set that the volume is based on is recovering from a loss of data
redundancy. The volume’s status changes from degraded to good as soon as the
recovery process in finished.
If a Disk Fails
If a RAID set or volume becomes degraded because a disk has failed, you can use RAID
Utility to identify the disk that needs to be replaced.
Note: If your RAID setup includes a spare drive, it is automatically incorporated into the
RAID set, and the set switches from degraded to good as soon as the recovery process
finishes. If there is no spare, the set will remain degraded until you replace the failed
drive, and if a second drive fails before you replace the first, you could lose data.
To replace a failed disk:
1 Open RAID Utility, select the RAID set or volume that is displaying a problem status
indicator, and look for a drive bay with a red status indicator.
The bay numbers in RAID Utility correspond to the numbered drive bays in your Mac
Pro or Xserve.
2 Replace the bad drive module.
3 Use the Make Spare command to set up the new drive as a global spare.
If no spare was available when the original drive failed, the RAID card uses the new
spare immediately to rebuild the affected RAID set and volumes. If a spare was
available at the time of the failure, it is already incorporated into the affected RAID set,
and the new spare remains available until it is needed.
If SMART Status is Listed as Unsupported
Self-Monitoring, Analysis, and Reporting Technology (SMART) status information is
available only for SATA drives. If you are using SAS drives, SMART is listed as
unsupported in the drive information in RAID Utility.
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Viewing the RAID System Log
If you have trouble with your RAID configuration, you can check the diagnostic
messages in the RAID log for more information. The RAID card and associated software
write status and diagnostic messages to /Library/Logs/CoreRAID.log.
To view the RAID log:
1 Open the Console application (in /Applications/Utilities/).
2 Click Logs in the toolbar.
3 Choose /Library/Logs/CoreRAID.log from the list on the left.
Using the Command Line
You can also set up and manage your RAID card from the command line using the
raidutil command. For information, see the raidutil man page or type raidutil at
the command-line prompt.
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About RAID Levels
RAID Utility lets you set up RAID sets based on the following RAID levels:
 Enhanced JBOD
 RAID 0 (striping)
 RAID 1 (mirroring)
 RAID 0+1 (mirroring a striped pair)
 RAID 5 (striping with distributed parity)
Enhanced JBOD
Using Enhanced JBOD, you can create a RAID set using a single drive. The resulting
RAID set doesn’t gain the performance or data protection of the other RAID levels, but
it does benefit from the data caching and battery backup provided by the RAID card.
An enhanced JBOD set can also be migrated to other RAID sets or moved to another
computer that has a Mac Pro or Xserve RAID Card installed.
RAID 0
RAID 0 offers improved performance but no data protection. Blocks of data are spread
across all of the drives in the RAID set in a process called striping. This allows better
performance because file contents move in parallel to and from the individual drives in
the set. RAID 0 also provides the most usable disk space; nearly all space on all drives is
available for user data. You can create a RAID 0 set using two, three, or four disks.
RAID 1
RAID 1 protects data against a drive failure and allows some increase in read
performance. Data is protected by duplicating the contents of each drive on a second
drive in the set, a process called mirroring. Because of the duplication, a volume based
on a RAID 1 set can’t be larger than half of the total space available on the drives in the
set. You can create a RAID 1 set using either two or four disks.
RAID 0+1
RAID 0+1 combines the performance of RAID 0 with the data protection of RAID 1 by
mirroring a striped set on a second pair of drives. Because mirroring duplicates all data,
this level offers less usable disk space than RAID 5. Usable space is half of the total
space available on the drives in the set. You need four disks to create a RAID 0+1 set.
RAID 5
RAID 5 is a compromise between the performance of RAID 0 and the data protection of
RAID 1. Performance is improved by striping data across the drives in the set. Data
protection is provided by parity information that is distributed across the drives. Data
can be recovered if any single drive fails. RAID 5 leaves you with more usable space
than RAID 1. RAID 5 needs only the equivalent of one drive’s worth of disk space to
store the parity information. You can create a RAID 5 set using either three or four disks.
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Using Non-RAID JBOD Disks
Disks that are not part of the RAID environment are called JBOD disks (just a bunch of
disks). If you install a new disk or a disk taken from a computer without a RAID card, it is
treated as a JBOD disk, and you see a dialog that asks you how you want to proceed.
Open Disk Utility: Opens Disk Utility so you can erase or partition the drive and then
use it in the Finder like any other disk. The resulting JBOD disk can also be read on a
computer that doesn’t have a RAID card installed.
Ignore: Allows a formatted disk to appear in the Finder with its data intact.
Open RAID Utility: Opens RAID Utility so you can use the disk to create a RAID set or a
spare drive. The disk is shown in RAID Utility with the state JBOD.
A non-RAID disk has
the state JBOD
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Setup Examples
The following examples show some common ways to set up RAID volumes.
Migrating to a Single RAID Volume
This is the easiest way to set up a RAID volume on a new computer. There’s no need to
reinstall the operating system or restore existing files on the computer’s startup disk.
However, the migration process does take some time and you can’t use the new
volume until the process is finished.
The example assumes that you have purchased a computer with a RAID card and four
500 GB disk drives. The computer is shipped with the operating system on the first disk.
With four disks, you can choose to migrate the existing startup volume to a RAID
volume based on a RAID 0, RAID 1, RAID 5, or RAID 0+1 scheme. For the best
combination of performance, protection, and volume size, you’ll choose RAID 5 for this
example. With RAID 5, roughly one drive’s worth of the space is dedicated to parity
data, so the usable space on the volume in this example will be roughly equivalent to
the total capacity of the three remaining disks.
To set up this example:
Start up the computer using the Mac OS X or Mac OS X Server installation disc that
comes with the computer. When the first Installer pane appears, you choose your
language and click Next. When the menu bar appears, you choose Utilities > RAID
Utility and then choose the Migrate RAID Set command. Finally, in the dialog that
appears, you choose Maximum Protection, make sure all three remaining drives are
selected, deselect “Create new volume using added capacity,” and click Migrate.
When the migration process finishes, you’ll have a single startup volume and additional
space on the new RAID set for creating additional volumes.
Migrating to Separate Startup and Data Volumes
This is similar to the previous example, except that in this case, you end up with two
volumes instead of one. The first volume will be the startup disk for the computer and
the second is available for general use.
To set up this example:
You perform the same steps as in the previous example, except that you select “Create
new volume using added capacity” in the migration options.
When the migration process finishes, you’ll have a startup volume and an empty data
volume.
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Creating a Separate High Performance Data Volume
As in the previous two examples, we’ll assume that you’ve purchased a computer with
a RAID card and four 500 GB disk drives. In this example, you want to take advantage of
RAID to create a fast data volume (for video editing, perhaps) and aren’t worried about
data protection. You’ll leave the current startup disk as is, and use a RAID 0 scheme to
create a separate volume on the remaining disks. RAID 0, which stripes data across the
drives in the RAID set, usually offers the highest performance. However, neither the
startup disk nor the data volume benefit from any data protection.
To set up this example:
First, because we’re leaving the original startup disk untouched, there’s no need to
restart the computer from a different disc; just open RAID Utility and use the Create
RAID Set command to create a RAID 0 set using the three remaining disks. When the
RAID set appears in the list on the left side of the RAID Utility window, select it and use
the Create Volume command to create the volume. The result is a fast 1,500 GB data
volume that is independent of the computer’s startup disk.
Creating a New Startup Volume and Several Data Volumes
In this example, you’ll recreate a startup volume, add several data volumes, and save
some space for a future volume, all on a protected RAID set that has a spare drive
available. As in the previous two examples, we’ll assume that you’ve purchased a
computer with a RAID card and four 500 GB disk drives.
To set up this example:
Because you’re going to recreate the current startup disk, you need to restart the
computer using the installation disc that comes with your computer and open RAID
Utility from the Utilities menu. Next, for the protection of the new startup disk and the
data volumes, you create a single RAID 5 set. To do so, choose the Create RAID Set
command, then choose RAID 5, select three of the four available disks, select the “Use
unassigned drives as spares” option, and click Create. Then, select the RAID set and use
the Create Volume command to create a 20 GB startup volume by changing the default
size in the volume creation dialog. Repeat the volume creation process to add other
data volumes with sizes that suit your needs. Finally, install Mac OS X or Mac OS X
Server on the new startup volume using the installation disc that comes with your
computer.
© 2007 Apple Inc. All rights reserved.
Apple, the Apple logo, Mac, Mac OS, and Xserve are trademarks
of Apple Inc., registered in the U.S. and other countries.
019-0972-A/07-2007