Using Software RAID1 Devices for Data Fault Tolerance
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novdocx (en) 6 April 2007
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5
Using Software RAID1 Devices for
Data Fault Tolerance
NetWare
®
Traditional File System volumes can span multiple disks. If a single disk fails, all
Traditional volumes that have segments on that disk also fail. To increase the data fault tolerance of
a server that has a Traditional file system, you can mirror the data from a Traditional NetWare
partition on one disk to Traditional NetWare partitions on other disks.
This section discusses the following:
Section 5.1, “Planning Your Software RAID1 Device,” on page 35
Section 5.2, “Managing Traditional Software RAID1 Devices,” on page 37
5.1 Planning Your Software RAID1 Device
Mirroring is a software RAID1 technique that writes data in parallel to multiple separate devices. If
one device fails, the other member devices remain available.
You can create a software RAID1 device with up to four member partitions, including the original
partition and up to three mirrored partitions. Each member partition resides on a separate server
disk.
As contrasted to a hardware RAID1 device, the server operating system controls the mirroring
activity in a software RAID1 device, which can slightly impact the CPU performance for the server.
Adding additional mirrors after the first contributes to availability, but it also incrementally impacts
CPU performance.
Typically, you write only to the original partition and send duplicate writes to the mirrored
partitions. However, you can read from all member partitions. This improves the read performance
of your Traditional volumes that contain volume segments in member partitions of the RAID.
This section discusses the following considerations for achieving fault tolerance:
Section 5.1.1, “Fault Tolerance for Traditional Volumes,” on page 35
Section 5.1.2, “Key Concepts for Mirroring Traditional NetWare Partitions,” on page 36
Section 5.1.3, “Improving Fault Tolerance for Software RAID1 Devices with Duplexing,” on
page 36
Section 5.1.4, “Example Software RAID1 Solution for Fault Tolerance of Traditional
Volumes,” on page 37
5.1.1 Fault Tolerance for Traditional Volumes
If you mirror one partition, you do not necessarily provide data protection for the entire volume. To
create software RAID1 devices for Traditional NetWare partitions, you must keep in mind the
relationship between Traditional NetWare partitions, volumes, and volume segments. (For
information about these key concepts, see Chapter 1, “Overview of the NetWare Traditional File
System,” on page 11.)
