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Managing Software RAIDs with
6
EVMS
This section describes how to create and manage software RAIDs with the Enterprise Volume
Management System (EVMS). EVMS supports only RAIDs 0, 1, 4, and 5 at this time. For RAID 6
and 10 solutions, see
Chapter 7, "Managing Software RAIDs 6 and 10 with mdadm," on page
Section 6.1, "Understanding Software RAIDs on Linux," on page 77
Section 6.2, "Creating and Configuring a Software RAID," on page 83
Section 6.3, "Expanding a RAID," on page 87
Section 6.4, "Adding or Removing a Spare Disk," on page 88
Section 6.5, "Managing Disk Failure and RAID Recovery," on page 89
Section 6.6, "Monitoring Status for a RAID," on page 92
Section 6.7, "Deleting a Software RAID and Its Data," on page 97
6.1 Understanding Software RAIDs on Linux
Section 6.1.1, "What Is a Software RAID?," on page 77
Section 6.1.2, "Overview of RAID Levels," on page 78
Section 6.1.3, "Comparison of RAID Performance," on page 79
Section 6.1.4, "Comparison of Disk Fault Tolerance," on page 79
Section 6.1.5, "Configuration Options for RAIDs," on page 80
Section 6.1.6, "Interoperability Issues," on page 80
Section 6.1.7, "Guidelines for Component Devices," on page 81
Section 6.1.8, "RAID 5 Algorithms for Distributing Stripes and Parity," on page 82
Section 6.1.9, "Multi-Disk Plug-In for EVMS," on page 83
Section 6.1.10, "Device Mapper Plug-In for EVMS," on page 83
6.1.1 What Is a Software RAID?
A RAID combines multiple devices into a multi-disk array to provide resiliency in the storage
device and to improve storage capacity and I/O performance. If a disk fails, some RAID levels keep
data available in a degraded mode until the failed disk can be replaced and its content reconstructed.
A software RAID provides the same high availability that you find in a hardware RAID. The key
operational differences are described in the following table:
Comparison of Software RAIDs and Hardware RAIDs
Table 6-1
Feature
RAID function
Linux Software RAID
Multi-disk (
) driver or
md
mdadm
Hardware RAID
RAID controller on the disk array
Managing Software RAIDs with EVMS
6
99.
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