Q316298: HOW TO: Choose a Volume Type for Your Windows NT Environment
Article: Q316298
Product(s): Microsoft Windows NT
Version(s): 4.0
Operating System(s):
Keyword(s): kbAudITPro kbHOWTOmaster
Last Modified: 09-APR-2002
-------------------------------------------------------------------------------
The information in this article applies to:
- Microsoft Windows NT Workstation version 4.0
- Microsoft Windows NT Server version 4.0
-------------------------------------------------------------------------------
IN THIS TASK
------------
- SUMMARY
- Overview of Windows NT 4.0 Volume Types
- Stripe Set
- Volume Set
- Stripe Set with Parity
- Mirror Set
- How to Choose a Volume Type for Your Windows NT 4.0 Environment
- How to Choose a Volume Type When You Require Fault Tolerance
- How to Choose a Volume Type When You Do Not Require Fault Tolerance
- REFERENCES
SUMMARY
=======
This step-by-step article describes how to choose between a stripe set, a volume
set, a stripe set with parity, and a mirror set. This article includes a brief
overview of each of these different volume types, and then it describes the
criteria to help you decide which volume type to use in your Windows NT 4.0
environment.
NOTE: Windows NT 4.0 Workstation natively supports only stripe sets (RAID 0) and
volume sets at the software level. Only Windows NT 4.0 Server natively supports
all of these disk configurations.
Overview of Windows NT 4.0 Volume Types
---------------------------------------
This section describes the four different volume types that you can use in a
Windows NT 4.0 environment.
Stripe Set:
A stripe set (which is commonly known as RAID 0) consists of equal-sized areas of
free space on at least 2 disks to as many as 32 disks that are combined in a
single volume. When data is written to a stripe set, it is written evenly across
all of the disks, one row at a time, in 64-kilobyte (KB) units. When you use a
stripe set, you can store a larger amount of data than when you use a single
disk. If the computer's disks are accessed simultaneously, a stripe set
increases the speed of read actions and write actions to the disks because
concurrent input/output (I/O) commands can be issued and processed on all disks
simultaneously. A stripe set does not provide any fault tolerance because there
is no data redundancy. The system and the boot partitions cannot be part of a
stripe set.
Volume Set:
A volume set consists of at least 2 areas and as many as 32 areas of unformatted
free space on one or more disks that are combined into a single volume. These
free spaces form one large logical volume set, which is treated as a single
partition. The areas of free space do not have to be identical in size. When you
use a volume set, data is written to one area at a time until no space remains
on it, and then data is written to the next member of the volume set, and so on.
When you use a volume set, you can store a larger amount of data than if you use
a single disk volume. The volume set is extensible, which means that Windows can
easily add data to the volume set. You do not increase speed performance if you
use a volume set instead of a single disk volume. A volume set does not provide
any fault tolerance because there is no data redundancy. The system and boot
partitions cannot be part of a volume set.
Stripe Set with Parity:
A stripe set with parity (which is commonly known as RAID 5) consists of
equal-sized areas of free space on at least 3 disks and as many as 32 disks that
are combined into a single, fault-tolerant volume. Like a stripe set and a
volume set, a stripe set with parity provides a means to store a larger amount
of data than a single disk can hold. Windows can read data from a stripe set
with parity faster than from a mirror set. However, a stripe set with parity
requires more system memory than a mirror set because of the parity
calculations. Fault tolerance is achieved in a stripe set with parity because
Windows NT writes parity information across each disk in the set. If a single
disk in the set fails, data is not lost because data from the failed disk can be
regenerated from the data and the parity information on each of the remaining
disks in the set. (However, if a disk fails, the read performance slows
considerably because data must be recovered by using parity information.) The
system partition and the boot partitions cannot be part of a stripe set with
parity.
Mirror Set:
A mirror set (which is commonly known as RAID 1) is a set of two equal-sized
partitions that are exact duplicates of each other. These two partitions are
located on two separate disks. The term "disk mirroring" refers to mirror set
use. When data is written to a mirror set, it is written to both partitions. A
mirror set provides good read performance and good write performance; however,
the mirror set does not read and write data as fast as a stripe set with parity.
Of all the Windows NT 4.0 volume types, a mirror set provides the highest level
of fault tolerance because data is duplicated in its entirety on to a separate
disk. (It is also the most expensive volume type because disk space use is only
50 percent.) Any partition, including the boot or system partition, can be
mirrored.
How to Choose a Volume Type for Your Windows NT 4.0 Environment
---------------------------------------------------------------
There are many factors that may influence your choice of volume type. The most
important factor is fault tolerance, which is the ability of a computer or an
operating system to respond to a catastrophic event, such as a power outage or a
hardware failure, so that no data is lost and any work in progress is not
corrupted. To decide the type of volume to use in your Windows NT 4.0
environment, you must decide if you require fault tolerance. If you require
fault tolerance, follow the procedure that is described in the "How to Choose a
Volume Type When You Require Fault Tolerance" section of this article. If you do
not require fault tolerance, use the procedure that is described in the "How to
Choose a Volume Type When You Do Not Require Fault Tolerance" section of this
article.
How to Choose a Volume Type When You Require Fault Tolerance:
To choose a volume type when you require fault tolerance:
1. Decide if you want to use either a stripe set with parity or a mirror set
(both volumes provide fault tolerance).
The following table compares and contrasts these two volume types:
+------------------------------------------------------------------------------------------------------------------------------------------+
| Stripe Set with Parity | Mirror Set |
+------------------------------------------------------------------------------------------------------------------------------------------+
| Supports FAT and NTFS | Supports FAT and NTFS |
+------------------------------------------------------------------------------------------------------------------------------------------+
| Cannot stripe the system or boot partition | Can mirror the system or boot partition |
+------------------------------------------------------------------------------------------------------------------------------------------+
| Requires a minimum of 3 hard disks | Requires 2 hard disks |
+------------------------------------------------------------------------------------------------------------------------------------------+
| Has lower cost per megabyte (MB) | Has higher cost per megabyte (MB)
(50 percent disk utilization) |
+------------------------------------------------------------------------------------------------------------------------------------------+
| Has moderate write performance
Has excellent read performance | Has good read and write performance |
+------------------------------------------------------------------------------------------------------------------------------------------+
| Requires more system memory for parity
calculations | Uses less system memory |
+------------------------------------------------------------------------------------------------------------------------------------------+
| Supports up to 32 hard disks | Supports exactly 2 hard disks |
+------------------------------------------------------------------------------------------------------------------------------------------+
| Is currently the most popular approach to
fault tolerance | Provides a higher level of fault tolerance
than a stripe set with parity |
+------------------------------------------------------------------------------------------------------------------------------------------+
2. Determine your priorities. Is fault tolerance your highest priority
(regardless of the cost)? Do you require only a modest amount of fault
tolerance (for a more modest cost)? Is I/O performance (or speed) your
highest priority?
If fault tolerance is your highest priority, it is recommended that you use a
mirror set for your Windows NT 4.0 environment. If either cost or speed is
your highest priority, it is recommended that you use a stripe set with
parity for your Windows NT 4.0 environment.
How to Choose a Volume Type When You Do Not Require Fault Tolerance:
To choose a volume type when you do not require fault tolerance:
1. Decide if you want to use either a stripe set or a volume set (both sets do
not provide any fault tolerance).
The following table compares the characteristics of these two volume types.
NOTE: The following acronyms are used in this table:
- IDE: Integrated development environment
- SCSI: Small computer system interface
- ESDI: Enhanced small device interface
+-------------------------------------------------------------------------------------------------------------------------------------+
| Condition | Stripe Set | Volume Set |
+-------------------------------------------------------------------------------------------------------------------------------------+
| Can it be created on one physical drive? | No | Yes |
+-------------------------------------------------------------------------------------------------------------------------------------+
| Can it contain the system or boot partition? | No | No |
+-------------------------------------------------------------------------------------------------------------------------------------+
| What is the maximum number of areas (partitions)
that can be combined? | 32 | 32 |
+-------------------------------------------------------------------------------------------------------------------------------------+
| Must the areas combined be of the same size? | Yes | No |
+-------------------------------------------------------------------------------------------------------------------------------------+
| Can it combine areas on different types of drives,
such as SCSI, ESDI, and IDE? | Yes | Yes |
+-------------------------------------------------------------------------------------------------------------------------------------+
| Is the area on one physical drive filled before the volume type
starts to fill the next physical drive? | No | Yes |
+-------------------------------------------------------------------------------------------------------------------------------------+
| Can it improve I/O performance? | Yes | No |
+-------------------------------------------------------------------------------------------------------------------------------------+
| Is the volume type easily extended? | No | Yes |
+-------------------------------------------------------------------------------------------------------------------------------------+
2. Determine your priorities.
Is I/O performance (speed) your highest priority? Or is extensibility your
highest priority? The costs associated with a stripe set and a volume set are
similar.
If performance speed is your highest priority, it is recommended that you use
a stripe set for your Windows NT 4.0 environment.
If extensibility is your highest priority, it is recommended that you use a
volume set for your Windows NT 4.0 environment.
REFERENCES
==========
For more information about the Windows NT 4.0 volume types, see Modules 6 and 7
of Microsoft Official Curriculum, Course Number 922.
For additional information about how to configure a stripe set with parity, click
the article number below to view the article in the Microsoft Knowledge Base:
Q316304 How to Configure a Stripe Set with Parity on a Windows NT Server 4.0
Computer
For additional information about how to configure a mirror set, click the article
number below to view the article in the Microsoft Knowledge Base:
Q316311 How to Configure a Mirror Set on a Windows NT Server 4.0 Computer
Additional query words:
======================================================================
Keywords : kbAudITPro kbHOWTOmaster
Technology : kbWinNTsearch kbWinNTWsearch kbWinNTW400 kbWinNTW400search kbWinNT400search kbWinNTSsearch kbWinNTS400search kbWinNTS400
Version : :4.0
Issue type : kbhowto
=============================================================================
THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY.
Copyright Microsoft Corporation 1986-2002.