How Do RAID-1 Volumes Work?
Solaris Volume Manager uses virtual disks to manage physical disks and their
associated data. In Solaris Volume Manager, a virtual disk is called a
volume. A volume is a name for a group of physical slices
that appear to the system as a single, logical device. Volumes are actually
pseudo, or virtual, devices in standard UNIX®
terms.
A volume is functionally identical to a physical disk in the view
of an application or a file system (such as UFS). Solaris Volume
Manager converts I/O requests that are directed at a volume into I/O
requests to the underlying member disks. Solaris Volume Manager volumes are built
from slices (disk partitions) or from other Solaris Volume Manager volumes.
You use volumes to increase performance and data availability. In some instances,
volumes can also increase I/O performance. Functionally, volumes behave the same way
as slices. Because volumes look like slices, they are transparent to end
users, applications, and file systems. Like physical devices, you can use Solaris
Volume Manager software to access volumes through block or raw device names. The
volume name changes, depending on whether the block or raw device is used.
The custom JumpStart installation method and Solaris Live Upgrade support the use of
block devices to create mirrored file systems. See RAID Volume Name Requirements and Guidelines for Custom JumpStart and Solaris Live Upgrade for details about
volume names.
When you create RAID-1 volumes ) with RAID-0 volumes (single-slice concatenations), Solaris Volume
Manager duplicates data on the RAID-0 submirrors and treats the submirrors as one
volume.
Figure 8-1 shows a mirror that duplicates the root (/) file system over two physical
disks.
Figure 8-1 Creating RAID-1 Volumes on the Root (/) File System on Two Disks
Figure 8-1 shows a system with the following configuration.
The mirror that is named d30 consists of the submirrors that are named d31 and d32. The mirror, d30, duplicates the data in the root (/) file system on both submirrors.
The root (/) file system on hdisk0 is included in the single-slice concatenation that is named d31.
The root (/) file system is copied to the hard disk named hdisk1. This copy is the single-slice concatenation that is named d32.
