Transactional Volumes

A transactional volume is a volume that is used to manage file system logging, which is essentially the same as UFS logging. Both methods record UFS updates in a log before the updates are applied to the file system.

A transactional volume consists of two devices:

• The master device is a slice or volume that contains the file system that is being logged.

• The log device is a slice or volume that contains the log and can be shared by several file systems. The log is a sequence of records, each of which describes a change to a file system.

A log device or a master device can be a physical slice or a volume. However, to improve reliability and availability, use RAID 1 volumes (mirrors) for log devices. A device error on a physical log device could cause data loss. You can also use RAID 1 or RAID 5 volumes as master devices.

Logging begins automatically when the transactional volume is mounted, provided the transactional volume has a log device. The master device can contain an existing UFS file system (because creating a transactional volume does not alter the master device). Or, you can create a file system on the transactional volume later. Likewise, clearing a transactional volume leaves the UFS file system on the master device intact.

After you configure a transactional volume, you can use it as though it were a physical slice or another logical volume. For information about creating a transactional volume, see Creating Transactional Volumes.