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COMPAQ CONFIDENTIAL
Writer: John Turner File Name: a-frnt
Codename: adg2 Part Number: 283954-001 Last Saved On: 5/22/02 12:40 PM
Compaq Advanced Data Guarding
Option Software
Reference Guide
Part Number 283954-001
May 2002 (First Edition)
COMPAQ CONFIDENTIAL
Writer: John Turner File Name: a-frnt
Codename: adg2 Part Number: 283954-001 Last Saved On: 5/22/02 12:40 PM
© 2002 Compaq Information Technologies Group, L.P.
Compaq and the Compaq logo are trademarks of Compaq Information Technologies Group,
L.P. in the U.S. and/or other countries. Microsoft, Windows, and Windows NT are trademarks
of Microsoft Corporation in the U.S. and/or other countries.
All other product names mentioned herein may be trademarks of their respective companies.
Compaq shall not be liable for technical or editorial errors or omissions contained herein. The
information in this document is provided “as is” without warranty of any kind and is subject to
change without notice. The warranties for Compaq products are set forth in the express limited
warranty statements accompanying such products. Nothing herein should be construed as
constituting an additional warranty.
Compaq Advanced Data Guarding Option Software Reference Guide
May 2002 (First Edition)
Part Number 283954-001
Compaq Advanced Data Guarding Option Software Reference Guide iii
COMPAQ CONFIDENTIAL
Writer: John Turner File Name: a-frnt
Codename: adg2 Part Number: 283954-001 Last Saved On: 5/22/02 12:40 PM
Contents
About This Guide
Symbols in Text...................................................................................................................v
Text Conventions .............................................................................................................. vi
Getting Help ...................................................................................................................... vi
Compaq Technical Support......................................................................................... vi
Compaq Website........................................................................................................ vii
Compaq Authorized Reseller..................................................................................... vii
Reader’s Comments ......................................................................................................... vii
Chapter 1
Overview of RAID ADG
Comparing RAID ADG to Other RAID Methods........................................................... 1-2
Probability of Logical Drive Failure......................................................................... 1-3
Choosing a RAID Method............................................................................................... 1-5
Chapter 2
System Setup
Enabling RAID ADG ...................................................................................................... 2-1
Configuring the System with RAID ADG ...................................................................... 2-3
Configuring a New System....................................................................................... 2-3
Migrating an Existing Logical Drive to RAID ADG................................................ 2-5
Migrating a RAID ADG Volume to Another Controller.......................................... 2-7
Assigning Online Spares after System Configuration..................................................... 2-7
Performance Tuning ........................................................................................................ 2-8
Changing the Cache Read/Write Ratio ..................................................................... 2-9
Optimizing the Stripe Size ........................................................................................ 2-9
Contents
iv Compaq Advanced Data Guarding Option Software Reference Guide
COMPAQ CONFIDENTIAL
Writer: John Turner File Name: a-frnt
Codename: adg2 Part Number: 283954-001 Last Saved On: 5/22/02 12:40 PM
Compaq Advanced Data Guarding Option Software Reference Guide v
COMPAQ CONFIDENTIAL
Writer: John Turner File Name: a-frnt
Codename: adg2 Part Number: 283954-001 Last Saved On: 5/22/02 12:40 PM
About This Guide
This guide provides step-by-step instructions for installation, and reference
information for operation, troubleshooting, and future upgrades for the Compaq
Advanced Data Guarding Option Software.
Symbols in Text
These symbols may be found in the text of this guide. They have the following
meanings.
WARNING: Text set off in this manner indicates that failure to follow directions
in the warning could result in bodily harm or loss of life.
CAUTION: Text set off in this manner indicates that failure to follow directions could
result in damage to equipment or loss of information.
IMPORTANT: Text set off in this manner presents clarifying information or specific
instructions.
NOTE: Text set off in this manner presents commentary, sidelights, or interesting points of
information.
About This Guide
vi Compaq Advanced Data Guarding Option Software Reference Guide
COMPAQ CONFIDENTIAL
Writer: John Turner File Name: a-frnt
Codename: adg2 Part Number: 283954-001 Last Saved On: 5/22/02 12:40 PM
Text Conventions
This document uses the following conventions:
• Italic type is used for complete titles of published guides or variables. Variables
include information that varies in system output, in command lines, and in
command parameters in text.
• Bold type is used for emphasis, for onscreen interface components (window
titles, menu names and selections, button and icon names, and so on), and for
keyboard keys.
•
Monospace typeface is used for command lines, code examples, screen
displays, error messages, and user input.
•
Sans serif typeface is used for uniform resource locators (URLs).
Getting Help
If you have a problem and have exhausted the information in this guide, you can get
further information and other help in the following locations.
Compaq Technical Support
In North America, call the Compaq Technical Support Phone Center at
1-800-OK-COMPAQ. This service is available 24 hours a day, 7 days a week. For
continuous quality improvement, calls may be recorded or monitored. Outside North
America, call the nearest Compaq Technical Support Phone Center. For telephone
numbers of worldwide Technical Support Centers, go to
www.compaq.com.
Be sure to have the following information available before you call Compaq:
• Technical support registration number (if applicable)
• Product serial number
• Product model name and number
• Applicable error messages
• Add-on boards or hardware
About This Guide
Compaq Advanced Data Guarding Option Software Reference Guide vii
COMPAQ CONFIDENTIAL
Writer: John Turner File Name: a-frnt
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• Third-party hardware or software
• Operating system type and revision level
Compaq Website
For information on this product, as well as the latest drivers and flash ROM images,
go to
www.compaq.com.
Compaq Authorized Reseller
For the name of your nearest Compaq authorized reseller:
• In the United States, call 1-800-345-1518.
• In Canada, call 1-800-263-5868.
• Elsewhere, see the Compaq website for locations and telephone numbers.
Reader’s Comments
Compaq welcomes your comments on this guide. Please send your comments and
suggestions by email to
Compaq Advanced Data Guarding Option Software Reference Guide 1-1
COMPAQ CONFIDENTIAL
Writer: John Turner File Name: b-ch1 overview of RAID ADG
Codename: adg2 Part Number: 283954-001 Last Saved On: 5/22/02 12:41 PM
1
Overview of RAID ADG
Advanced Data Guarding (RAID ADG) is a fault-tolerance method that uses two
different and independent sets of parity data. A logical volume using this
exceptionally high level of data protection can tolerate the simultaneous failure of
two hard drives without suffering downtime or data loss.
B1
B3
P5,6
Q7,8
B2
B7
P3,4
Q5,6
B5
B8
P1,2
Q3,4
B4
B6
P7,8
Q1,2
Figure 1-1: Array using RAID ADG, showing data blocks
(B) and two parity data sets (P, Q)
RAID ADG also makes efficient use of drive space, since the two sets of parity data
occupy a total drive space equivalent to two hard drives. The amount of drive space
used for parity data is independent of the total number of hard drives in the logical
volume.
Overview of RAID ADG
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Theoretically, RAID ADG can support a logical volume that spans over 200 hard
drives without any great risk of data loss. However, currently existing array
controllers and storage systems support no more than 14 drives per channel. Thus, the
largest obtainable logical volume, using a 4-channel controller, spans 56 hard drives.
Comparing RAID ADG to Other RAID Methods
Table 1-1 summarizes the most important features of the different RAID methods
that are supported by Compaq array controllers. For more detailed information, refer
to the user guide for the Smart Array controller that is installed in the system.
Table 1-1: Comparison of RAID Methods
RAID 0 RAID 1+0 RAID 5 RAID ADG
Alternative name Striping (no
fault tolerance)
Mirroring Distributed
Data Guarding
Advanced Data
Guarding
Usable drive space* 100% 50% 67% to 93% 50% to 96%
Usable drive space
formula
n n/2 (n-1)/n (n-2)/n
Minimum number of
physical drives
1 2 3 4
Tolerates failure of
one physical drive?
No Yes Yes Yes
Tolerates
simultaneous failure
of more than one
physical drive?
No Only if no two
failed drives are
in a mirrored pair
No Yes
Read performance High High High High
Write performance High Medium Low Low
Relative cost Low High Medium Medium
*Values for usable drive space are calculated with these assumptions: (1) All physical drives in the
array have the same capacity; (2) Online spares are not used; (3) No more than 14 physical drives
are used per array for RAID 5; (4) No more than 56 drives are used with RAID ADG.
Overview of RAID ADG
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Probability of Logical Drive Failure
The probability that a logical drive will fail depends on the RAID level setting.
• A RAID 0 logical drive will fail if only one physical drive fails.
• For a RAID 1+0 logical drive, the failure situation is complex.
— The maximum number of physical drives that can fail without causing
failure of the logical drive is n/2, where n is the number of hard drives in the
array. This maximum is reached only if no failed drive is mirrored to any
other failed drive. In practice, a logical drive usually fails before this
maximum is reached. As the number of failed physical drives increases, it
becomes increasingly unlikely that a newly failed drive is not mirrored to a
previously failed drive.
— The failure of only two physical drives is enough to cause a logical drive to
fail if the two drives happen to be mirrored to each other. The risk of such
mutually mirrored drives failing decreases as the number of mirrored pairs in
the array increases.
• A RAID 5 logical drive (with no online spare) fails if two physical drives fail.
• A RAID ADG logical drive (with no online spare) fails when three physical
drives fail.
At any given RAID level, the probability of logical drive failure increases as the
number of physical drives in the logical drive increases.
The graph in Figure 1-2 provides more quantitative information. The data for this
graph is calculated from the mean time between failure (MTBF) value for a typical
physical drive, assuming that no online spares are present. If an online spare is added
to any of the fault-tolerant RAID configurations, the probability of logical drive
failure is further decreased.
Overview of RAID ADG
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Figure 1-2: Relative probability of logical drive failure
for different RAID levels
1 6 11 16 21 26 31 36 41 46 51 56
Total number of physical drives in array
Increasing likelihood of logical drive failure > > >
RAID 0
RAID 5
RAID 1+0
RAID ADG
Overview of RAID ADG
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Writer: John Turner File Name: b-ch1 overview of RAID ADG
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Choosing a RAID Method
There are three primary reasons for using RAID ADG:
• You need greater fault tolerance than RAID 5 can provide but you also want to
use as much drive space as possible for data.
• You need to use a greater percentage of drive space for data than with RAID 1+0
while maintaining a high level of fault tolerance.
• You need a large logical volume, incorporating over ten hard drives.
Table 1-2 may help you to decide which RAID option is best for your situation.
Table 1-2: Choosing a RAID Method
Most Important Also Important Suggested RAID Level
Fault tolerance Cost effectiveness RAID ADG
I/O performance RAID 1+0
Cost effectiveness Fault tolerance RAID ADG
I/O performance
RAID 5 (RAID 0 if fault
tolerance is not required)
I/O performance
Cost effectiveness
RAID 5 (RAID 0 if fault
tolerance is not required)
Fault tolerance RAID 1+0
Compaq Advanced Data Guarding Option Software Reference Guide 2-1
COMPAQ CONFIDENTIAL
Writer: John Turner File Name: c-ch2 system setup
Codename: adg2 Part Number: 283954-001 Last Saved On: 5/22/02 12:42 PM
2
System Setup
Enabling RAID ADG
Before you can configure an array with RAID ADG, you must enable the array
controller to use this feature. The most convenient method of doing this is to install a
software key on the server.
NOTE: Older versions of the Smart Array 5300 Controller can also be enabled for RAID ADG
by a hardware enabler module that plugs into the array controller board. Either method of
enabling this model of controller is valid.
To install the software key:
1. Review the list of features in the array controller user guide to confirm that the
array controller supports RAID ADG, and confirm that the array accelerator has
a capacity of at least 64 MB.
2. Close all applications and utilities on the server containing the array controller.
3. Insert the RAID ADG option software kit CD into the CD-ROM drive.
4. Reboot the server.
5. If necessary, upgrade the controller firmware to the version provided on the CD,
and then reboot the server. (This step is required, for example, if the controller is
a Smart Array 5300 with a current firmware version less than 2.72.)
NOTE: If the firmware on the controller is newer than that on the CD, the flash utility does
not replace it with the earlier firmware from the CD.
6. Select Array Configuration Utility XE from the CD menu.
System Setup
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This action opens ACU-XE, the browser-based version of the Compaq Array
Configuration Utility (ACU).
IMPORTANT: Use the version of ACU-XE that is provided on the CD. The software key
cannot be installed using versions of ACU-XE earlier than 1.40, nor can it be installed
using ACU.
7. When the utility has loaded, select the controller that is to be used to configure
RAID ADG.
8. Select License Key Management.
9. Select Enter License Key.
10. Enter the 25-character software key (provided on the CD sleeve) and click
Submit.
If you wish, you may now configure the controller using ACU-XE.
11. Exit ACU-XE, remove the CD, and reboot the server.
For further instructions or clarifications regarding the software key installation
procedure, refer to the ACU-XE online help.
After you have enabled RAID ADG (whether by software key or hardware enabler
module), you can configure the array controller. This can be achieved using either
ACU or ACU-XE; both are equally suitable. Most of the configuration instructions
described in the remaining sections of this chapter assume that you are using ACU.
NOTE: For more detailed information about ACU, refer to the user guide provided with the
array controller. For more detailed information about ACU-XE, refer to the Array Configuration
Utility XE User Guide that is provided in the RAID ADG option software kit.
If you decide to use ACU, check that the latest version is installed on the system
before beginning any configuration procedure:
1. Refer to
www.compaq.com and locate the page containing the current ACU file.
2. Note the version number of this file.
3. Compare this version number with that of the ACU file that is already installed
on the system.
4. Download the newer version and install it on the system, if necessary.
System Setup
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Configuring the System with RAID ADG
The procedure for configuring a system with RAID ADG depends on whether it is a
new system and what operating system it uses. This section gives an overview of the
procedure. For more detailed information, refer to the user guide for the array
controller that the system is using.
NOTE: The maximum size of a logical drive that can be configured through ACU is 2 TB.
However, some operating systems do not support logical drives that are larger than 502 GB.
Refer to the operating system documentation for details.
Configuring a New System
Windows NT and Windows 2000
There are three main steps to configure a new system for RAID ADG:
1. Set up an array.
2. Assign hard drives to the array.
3. Create logical drives within the array.
Setting Up an Array
1. Double-click the ACU icon on the desktop.
2. Select the controller from the drop-down list in the top left corner of the main
ACU screen.
3. Click Settings in the Controller box in the top right corner of the main ACU
screen.
4. Set the rebuild priority, expansion priority, and accelerator ratio.
5. Click Done to activate the settings and return to the main ACU screen.
Assigning Hard Drives to the Array
1. Click Create Array in the Controller box.
System Setup
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2. Select the hard drives that are to make up the array, remembering to leave any
that you want to use as online spares.
3. Click the Assign Drive to Array button in the upper middle part of the screen.
4. Select the hard drives that are to be used as online spares.
5. Click the Assign Spare to Array button in the lower middle part of the screen.
6. Click Done to activate the settings and return to the main ACU screen.
Creating a Logical Drive within the Array
1. Click the array icon on the main ACU screen.
2. Click Create Logical Drive in the Array box.
3. Select RAID ADG.
4. On the same screen, select Enable in the Array Accelerator box.
5. Change the stripe size, if required. The default setting is 16 Kbytes for
RAID ADG, suitable for most common uses. The “Optimizing the Stripe Size”
section discusses the stripe sizes that are most useful for various applications.
6. Change the logical drive size, if desired.
7. Click Done to activate the settings and return to the main ACU screen.
8. Select Save Configuration from the Controller menu.
9. Select Exit from the Controller menu.
NetWare
1. Visit the Novell website and check that the latest support pack or operating
system patch is installed on the system.
2. Visit the Compaq website and check that you have the latest drivers for the
controller that is installed in the system.
3. Open the CPQONLIN utility.
In a new system that has no logical drives configured, CPQONLIN opens to the
auto-configuration wizard.
System Setup
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4. If you want to use the wizard, select RAID ADG as the fault-tolerance level.
Alternatively, exit the wizard and custom configure the system.
5. Save the changes and exit CPQONLIN.
Migrating an Existing Logical Drive to RAID ADG
Before migrating a logical drive that is currently configured for RAID 0 or RAID 5,
you must expand the array. If the logical drive has a RAID 1 configuration, it does
not need to be expanded before migration.
IMPORTANT: Although data loss is not anticipated, Compaq recommends that you back up
all data before migrating a logical drive.
NOTE: Expansion and migration each take about 15 minutes per gigabyte. Data can still be
read from or written to any logical drive on the controller during an expansion or migration,
although performance might be reduced. However, a controller can perform only one
expansion, extension, or migration at any given time.
Windows NT and Windows 2000
Expanding the Array
1. Add at least one extra hard drive to the system if migrating from RAID 5, or
three extra hard drives if migrating from RAID 0. The capacity of each added
drive should be no less than that of the smallest hard drive currently used in the
logical volume.
2. Double-click the ACU icon on the desktop.
3. Select the controller from the drop-down list on the main ACU screen.
4. Select the array to be expanded from the configuration view box.
5. Click Expand in the Array box.
6. Select the extra hard drives that you added to the system, except any that you
want to be used as spares.
7. Click the Assign Drive to Array button in the upper middle part of the screen.
8. Select the online spares, if any are to be used.
System Setup
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COMPAQ CONFIDENTIAL
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9. Click the Assign Spare to Array button in the lower middle part of the screen.
10. Continue the migration when expansion has finished.
Migrating the Logical Drive
1. In ACU, click Migrate in the Logical Drive box in the lower right corner of the
main ACU screen.
2. Select RAID ADG on the Migrate RAID/Stripe Size screen that is displayed.
3. Change the stripe size, if required. The default setting is 16 Kbytes for
RAID ADG, suitable for most common uses. The “Optimizing the Stripe Size”
section discusses the stripe sizes that are most useful for various applications.
4. Click Done.
5. Select Save Configuration from the Controller menu.
6. Select Exit from the Controller menu.
NetWare
1. Visit the Novell website and check that the latest support pack or operating
system patch is installed on the system.
2. Visit the Compaq website and check that you have the latest drivers for the
controller that is installed in the system.
3. Add at least one extra hard drive to the system if you are migrating from RAID 5,
or three extra hard drives if you are migrating from RAID 0. The capacity of each
added drive should be no less than that of the smallest hard drive currently used
in the logical volume.
4. Open the CPQONLIN utility.
5. Expand the array if you are migrating from RAID 5 or RAID 0.
6. When array expansion has finished, select the logical drive that you want to
migrate to RAID ADG and press the Enter key.
7. Select Drive Settings on the Logical Drive menu.
8. Select RAID ADG from the list.
System Setup
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9. Change the stripe size if desired. The “Optimizing the Stripe Size” section
discusses the stripe sizes that are most useful for various applications.
10. Press the Esc key to save the changes and begin the migration.
Migrating a RAID ADG Volume to Another Controller
You can migrate a RAID ADG logical volume only if both controllers support RAID
ADG. If the new controller supports RAID ADG but does not have it enabled, the
write cache is disabled. In this case, though, the data can still be read or copied.
Assigning Online Spares after System Configuration
Assigning online spares to a fault-tolerant configuration provides additional
protection against hard drive failure.
You can:
• Assign a different online spare to each array on the controller.
• Share one online spare among several arrays on the same controller, for efficient
use of drive capacity.
• Assign several online spares to just one array.
• Share several online spares among several arrays; this method provides the
greatest amount of protection for the largest number of arrays.
IMPORTANT: Assigning several spares to an array lets you postpone replacement of faulty
drives, but it does not increase the fault-tolerance level of any logical drives in the array. For
example, a logical drive in a RAID 5 configuration suffers irretrievable data loss if two physical
drives fail simultaneously, regardless of the number of spare drives assigned.
Any drive that you assign as an online spare for an array operates as the spare for
every fault-tolerant logical drive within the array.
To assign online spares:
1. Check that at least one hard drive containing no data is connected to the
controller that contains the array.
System Setup
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2. Double-click the ACU icon on the desktop.
3. Select the controller from the drop-down list on the main ACU screen.
4. Select the array.
5. Click Modify in the Array box.
6. Select the drives that are to be used as online spares.
IMPORTANT: The capacity of an online spare should be no less than that of any other drive
in the same array. This must be true of every array that uses that drive as an online spare.
7. Click the Assign Spare to Array button in the lower middle part of the screen.
8. Click Done.
9. Click Settings in the Controller box on the main ACU screen.
10. In the Rebuild Priority box on the Controller Settings screen, select High if
rebuilding data is more important than handling operating system requests. If the
controller should rebuild data only when it is idle, select Low.
CAUTION: Selecting a high rebuild priority results in reduced server
performance while the rebuild is in progress. Selecting a low rebuild priority does
not affect server performance, since rebuilding then occurs only when the server
is idle. However, selecting a low rebuild priority greatly increases the time
required for a rebuild. This extended rebuild time substantially increases the risk
that another drive will fail before the rebuild has finished. If additional drive failure
occurs, fault tolerance may be compromised, and data may be irretrievably lost.
11. Click Done.
12. Select Save Configuration from the Controller menu.
13. Select Exit from the Controller menu.
Performance Tuning
There are several ways in which you can optimize the performance of the system:
• Change the ratio of cache memory allocated to reads and writes.
/