A Virtual I/O Server (VIOS) logical partition that is assigned to the shared memory pool (hereafter referred to as a paging VIOS partition) provides access to the paging space devices for the logical partitions that are assigned to the shared memory pool (hereafter referred to as shared memory partitions).
When the operating system that runs in a shared memory partition attempts to access data, and the data is located in the paging space device that is assigned to the shared memory partition, the hypervisor sends a request to a paging VIOS partition to retrieve the data and write it to the shared memory pool so that the operating system can access it.
A paging VIOS partition is not a shared memory partition and does not use the memory in the shared memory pool. A paging VIOS partition provides access to the paging space devices for the shared memory partitions.
On systems that are managed by the Integrated Virtualization Manager, the management partition is the paging VIOS partition for the shared memory partitions that are assigned to the shared memory pool. When you create the shared memory pool, you assign a paging storage pool to the shared memory pool. The paging storage pool provides the paging space devices for the shared memory partitions that are assigned to the shared memory pool.
If you configure the shared memory pool with two paging VIOS partitions, you can configure a shared memory partition to use either a single paging VIOS partition or redundant paging VIOS partitions. When you configure a shared memory partition to use redundant paging VIOS partitions, you assign a primary paging VIOS partition and a secondary paging VIOS partition to the shared memory partition. The hypervisor uses the primary paging VIOS partition to access the shared memory partition's paging space device. At this point, the primary paging VIOS partition is the current paging VIOS partition for the shared memory partition. The current paging VIOS partition is the paging VIOS partition that the hypervisor uses at any point in time to access data in the paging space device that is assigned to the shared memory partition. If the primary VIOS partition becomes unavailable, the hypervisor uses the secondary paging VIOS partition to access the shared memory partition's paging space device. At this point, the secondary paging VIOS partition becomes the current paging VIOS partition for the shared memory partition and continues as the current paging VIOS partition even after the primary paging VIOS partition becomes available again.
You do not need to assign the same primary and secondary paging VIOS partitions to all of the shared memory partitions. For example, you assign paging VIOS partition A and paging VIOS partition B to the shared memory pool. For one shared memory partition, you can assign paging VIOS partition A as the primary paging VIOS partition and paging VIOS partition B as the secondary paging VIOS partition. For a different shared memory partition, you can assign paging VIOS partition B as the primary paging VIOS partition and paging VIOS partition A as the secondary paging VIOS partition.
The following figure shows an example of a system with four shared memory partitions, two paging VIOS partitions, and four paging space devices.
The example shows the configuration options for paging VIOS partitions and paging space devices as described in the following table.
| Configuration option | Example |
|---|---|
| The paging space device that is assigned to a shared memory partition is located in physical storage in the server and is accessed by a single paging VIOS partition. | Paging space device 4 provides the paging space for Shared memory partition 4. Shared memory partition 4 is assigned to use Paging VIOS partition 2 to access Paging space device 4. Paging space device 4 is located in physical storage in the server and is assigned to Paging VIOS partition 2. Paging VIOS partition 2 is the only paging VIOS partition that can access Paging space device 4 (This relationship is shown by the blue line that connects Paging VIOS partition 2 to Paging space device 4.). |
| The paging space device that is assigned to a shared memory partition is located on a SAN and is accessed by a single paging VIOS partition. | Paging space device 1 provides the paging space for Shared memory partition 1. Shared memory partition 1 is assigned to use Paging VIOS partition 1 to access Paging space device 1. Paging space device 1 is connected to the SAN. Paging VIOS partition 1 is also connected to the SAN and is the only paging VIOS partition that can access Paging space device 1 (This relationship is shown by the green line that connects Paging VIOS partition 1 to Paging space device 1.). |
| The paging space device that is assigned to a shared memory partition is located on a SAN and is accessed redundantly by two paging VIOS partitions. | Paging space device 2 provides the paging space
for Shared memory partition 2. Paging space device 2 is connected
to the SAN. Paging VIOS partition 1 and Paging VIOS partition 2 are
also connected to the SAN and can both access Paging space device
2. (These relationships are shown by the green line that connects
Paging VIOS partition 1 to Paging space device 2 and the blue line
that connects Paging VIOS partition 2 to Paging space device 2.) Shared
memory partition 2 is assigned to use redundant paging VIOS partitions
to access Paging space device 2. Paging VIOS partition 1 is configured
as the primary paging VIOS partition and Paging VIOS partition 2 is
configured as the secondary paging VIOS partition. Similarly, Paging space device 3 provides the paging space for Shared memory partition 3. Paging space device 3 is connected to the SAN. Paging VIOS partition 1 and Paging VIOS partition 2 are also connected to the SAN and can both access Paging space device 3. (These relationships are shown by the green line that connects Paging VIOS partition 1 to Paging space device 3 and the blue line that connects Paging VIOS partition 2 to Paging space device 3.) Shared memory partition 3 is assigned to use redundant paging VIOS partitions to access Paging space device 3. Paging VIOS partition 2 is configured as the primary paging VIOS partition and Paging VIOS partition 1 is configured as the secondary paging VIOS partition. Because Paging VIOS partition 1 and Paging VIOS partition 2 both have access to Paging space device 2 and Paging space device 3, Paging space device 2 and Paging space device 3 are common paging space devices that are accessed redundantly by Paging VIOS partition 1 and Paging VIOS partition 2. If Paging VIOS partition 1 becomes unavailable and Shared memory partition 2 needs to access data on its paging space device, the hypervisor sends a request to Paging VIOS partition 2 to retrieve the data on Paging space device 2. Similarly, if Paging VIOS partition 2 becomes unavailable and Shared memory partition 3 needs to access the data on its paging space device, the hypervisor sends a request to Paging VIOS partition 1 to retrieve the data on Paging space device 3. |
| A paging VIOS partition accesses both independent and common paging space devices. | Paging space device 1 and Paging space device
4 are independent paging space devices because only one paging VIOS
partition accesses each. Paging VIOS partition 1 accesses Paging space
device 1, and Paging VIOS partition 2 accesses Paging space device
4. Paging space device 2 and paging space device 3 are common paging
space devices because both paging VIOS partitions access each. (These
relationships are shown by the green and blue lines that connect the
paging VIOS partitions to the paging space devices.) Paging VIOS partition 1 accesses the independent paging space device Paging space device 1, and also accesses the common paging space devices Paging space device 2 and Paging space device 3. Paging VIOS partition 2 accesses the independent paging space device Paging space device 4 and also accesses the common paging space devices Paging space device 2 and Paging space device 3. |
When a single paging VIOS partition is assigned to the shared memory pool, you must shut down the shared memory partitions before you shut down the paging VIOS partition so that the shared memory partitions are not suspended when they attempt to access their paging space devices. When two paging VIOS partitions are assigned to the shared memory pool and the shared memory partitions are configured to use redundant paging VIOS partitions, you do not need to shut down the shared memory partitions to shut down a paging VIOS partition. When one paging VIOS partition is shut down, the shared memory partitions use the other paging VIOS partition to access their paging space devices. For example, you can shut down a paging VIOS partition and install VIOS updates without shutting down the shared memory partitions.
You can configure multiple VIOS logical partitions to provide access to paging space devices. However, you can only assign up to two of those VIOS partitions to the shared memory pool at any given time.
After you configure the shared memory partitions, you can later change the redundancy configuration of the paging VIOS partitions for a shared memory partition by modifying the partition profile of the shared memory partition and restarting the shared memory partition with the modified partition profile:
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