Snapshot support
If you want to back up the primary environment without affecting normal functioning, you
need the additional support of an operating system snapshot.
On the Linux® platform, you can use Logical Volume Management (LVM). LVM provides a higher-level view of the disk storage on a computer system than the traditional view of disks and partitions. With LVM, the system administrator has more flexibility in allocating storage to applications and users by demand. The physical volumes of the disk are organized as logical volumes, and the file system is mounted on logical volumes. This organization allows the flexible and dynamic management of the disk size of the file system.
When you enable the snapshot function on the LVM, the file system supports concurrent backup
while the file system is undergoing a write operation.
Note: Without snapshot support, the native
backup of a large number of files consumes a great deal of time. During this period of time, some
files might be updated because transactions are continuing in the production environment, which
means that the backup contains files saved at different points in time. If any files are in an
inconsistent state, the backup is not acceptable.
To support the snapshot functionality through LVM, the Copy on Write mechanism is used. When Copy
on Write is used, the following sequence of events occurs:
- The snapshot creates a logical copy of the data after the application is frozen for a very short period.
- A write request to the original copy of the data results in the system copying the original data to the snapshot disk area before the original copy is overwritten.
- A read into the logical copy is redirected to the original copy if the data is not modified. If the data is modified, the read request is satisfied from the snapshot disk area.
The following topics provide information about taking the snapshot:
This topic only applies to BAW, and is located in the BAW repository. Last updated on 2025-03-13 12:15