Remote physical volume (RPV)
Remote physical volume (RPV) is a pseudo device driver and its kernel extension that allows the LVM to consider the physical volume located at the remote site as another local physical volume, although the actual data I/O operations are performed at the remote site.
You can mirror your data across two sites by configuring volume groups that contain both local and RPVs. With an RPV device driver, the LVM does not distinguish between local and remote physical volumes - it maintains mirror copies of the data across attached disks. The LVM is, for the most part, unaware that some disks are located at a remote site. During a disk read operation, however, the LVM tries to satisfy the read request from a local copy of the data (when available) to maximize performance. During a disk write operation the RPV device driver and LVM work together to allow the application to perform a single logical write that results in multiple physical writes to the local PVs and RPVs comprising the volume group.
The RPV consists of:
- The RPV client. The RPV client is a pseudo device driver that runs on the node on the local site, that is, on the node at a geographic location where your applications issue data I/O requests to the physical volumes.
- The RPV server. The RPV server is an instance of the kernel extension of the RPV device driver that runs on the node on the remote site, that is, on the node at a remote geographic location to which the data is mirrored over an IP-based network. The RPV client sends I/O requests to the RPV server.
The geographically mirrored volume group is a volume group that contains one or more logical volumes that have copies residing on RPVs.
After you configure geographically mirrored volume groups which contain RPVs, you can include them as replicated resources in PowerHA® SystemMirror®-managed resource groups in the PowerHA SystemMirror cluster that is configured across two sites.
The following figure illustrates the mirroring process that occurs between the RPV client and RPV server. The RPV client is configured on the node at site Waltham (the local site for the resource group) and the RPV server is configured on the node at site Austin (the remote site for the resource group):
