Logical Storage Manager

Digital UNIX Version 4.0 supports the Logical Storage Manager (LSM), a more robust logical storage manager than Logical Volume Manager (LVM), which it has replaced. LSM supports all of the following:

• Disk spanning

  Disk spanning allows you to concatenate entire disks or parts (regions) of multiple disks together to use as one, logical volume. So, for example, you could "combine" two RZ26s and have them contain the /usr file system.

• Mirroring

  Mirroring allows you to write simultaneously to two or more disk drives to protect against data loss in the event of disk failure.

• Striping

  Striping improves performance by breaking data into segments that are written to several different physical disks in a "stripe set."

• Comprehensive disk management capabilities

  LSM supports disk management utilities that, among other things, change the disk configuration without disrupting users while the system is up and running.

Mirroring, striping and the graphical interface require a separate license PAK. The LSM code came from VERITAS (the VERITAS Volume Manager) and was enhanced by Digital.

For each logical volume defined in the system, the LSM volume device driver maps logical volume I/O to physical disk I/O. In addition, LSM uses a user-level volume configuration daemon (vold) that controls changes to the configuration of logical volumes. Users can administer LSM either through a series of command-line utilities or by availing themselves of an intuitive Motif-based graphical interface.

To ensure a smooth migration from LVM to LSM, Digital has developed a migration utility that maps existing LVM volumes into nonstriped, nonmirrored LSM volumes that preserves all of the LVM data. After the migration is complete, administrators can mirror the volumes if they so desire.

Similarly, to help users transform their existing UFS or AdvFS partitions into LSM logical volumes, Digital has developed a utility that will transform each partition in use by UFS or AdvFS into a nonstriped, nonmirrored LSM volume. After the transformation is complete, administrators can mirror the volumes if they so desire.

Note that LSM volumes can be used in conjunction with AdvFS, as part of an AdvFS domain; with RAID disks; and with the Available Server Environment (ASE), since LSM supports logical volume failover. For more information on LSM, see the Logical Storage Manager .