Applications that directly access the local Linux file system see the primary file tree and the secondary file tree as independent directories. Thus, backup tools can apply one backup policy to the primary file tree and a different backup policy to the secondary file tree. The only operations that take place on the secondary volume are backup, or remove and archive.
Using shadow volumes allows backups of important data to be made faster and more frequently because you can apply different backup policies for the primary volume and secondary volume. For example, the server administrator can partition the volume’s data into two categories:
Important data that needs to be maintained on quality storage and backed up frequently.
Less important data that can be stored on less expensive storage and backed up less frequently.
An analysis or inventory of a volume’s data shows that a large portion of it is seldom used. Having a shadow volume allows the server administrator to spend more on the most important data and spend less on the less important data. The frequently used data can be backed up incrementally or fully each day. The seldom-used data can be backed up weekly or monthly. Getting the less important data out of the way enables the backups of your important data to run more quickly and efficiently. Partitioning your data in this way can significantly reduce the cost of hosting it.
Because the most important files are located in the primary storage area, disaster recovery can also be faster. The server administrator can restore the critical files by restoring the primary storage area first, then restore the secondary storage area. This lets the users quickly get the files they need most, and they do not need to wait while files they do not usually need are restored. In addition, more fault tolerant replication solutions can be deployed for the primary storage area where it matters most.
If you back up the NSS volume by using the NSS Extended Attributes (XAttr) settings to preserve the NetWare metadata (netware.metadata) for file system rights and attributes, this information can be restored only directly to an NSS volume. For information about using the NSS /ListXattrNWmetadata option and the security considerations involved, see ListXattrNWmetadata Option
in the OES 2 SP3: NSS File System Administration Guide for Linux.
Backup utilities might also work against the ShadowFS merged view. However, because the ShadowFS merged view is a Linux mount point and is not seen by the backup software as an NSS volume, the file system rights and attributes are not preserved. It is not recommended or supported to back up NSS files from this Linux mount point.