IBM BPM, V8.0.1, All platforms > Troubleshooting and support > Disaster recovery > Installation and configuration considerations > Operating system considerations
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.
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:
- Prepare the operating system before a snapshot
Before you take a snapshot of the operating system, you create a physical volume and logical volume.- Taking an operating system snapshot
As part of your disaster recovery plan, you create a snapshot of the operating system from your primary environment. You then transfer the snapshot to your secondary environment.