Information Technology Reference
In-Depth Information
Introduction
This chapter describes some of the advantages of virtual disk management
systems and briefly describes some of the techniques used by these systems
to improve availability. These include duplexing, mirroring, logging and disk
arrays. The features and key concepts of the virtual disk management system
included with Solaris 9, the Solaris Volume Manager, are described.
Virtual File Systems
Virtual disk management systems allow the use of physical disks in different
ways that are not supported by the standard Solaris file systems. This section
summarizes these advantages and describes several techniques used to pro-
vide virtual file systems.
Advantages of Virtual Disk Management
Systems
A virtual disk management system can overcome disk capacity and architec-
ture limitations and improve performance and availability. In addition, man-
ageability is enhanced by the use of a graphical management tool.
The three main storage factors are performance, availability, and hardware
costs. A virtual disk management system allows managing tradeoffs between
these three factors and in some cases reduces the impact of these factors.
Overcoming Disk Limitations
Virtual disk management systems allow partitions on multiple disks to be
combined and treated as a single partition. Not only does this allow file sys-
tems to be larger than the largest available physical disks, it also allows the
entire storage area on a physical disk to be used.
Improved Performance
Typically, using multiple disks in place of a single disk will increase perform-
ance by spreading the load across several physical disks.
Improved Availability
Virtual disk management systems typically support data-redundancy or high-
availability features, such as
mirroring
and
Redundant Arrays
of
Inexpensive
Disks
(
RAID
) configurations. In addition, features such as
hot sparing
and
file
system logging
reduce recovery time.
