Logical Domain Channels (LDCs) and Logical Domains

There is a limit to the number of LDCs available in any logical domain. For UltraSPARC T1 based platforms, that limit is 256. For all other platforms, the limit is 512. This only becomes an issue on the control domain because the control domain has at least part, if not all, of the I/O subsystem allocated to it. This might also be an issue because of the potentially large number of LDCs that are created for both virtual I/O data communications and the Logical Domains Manager control of the other logical domains.

The examples in this section are what happens on UltraSPARC T1 based platforms. However, the behavior is the same if you go over the limit on other supported platforms.

If you try to add a service, or bind a domain, so that the number of LDC channels exceeds the limit on the control domain, the operation fails with an error message similar to the following:

13 additional LDCs are required on guest primary to meet this request,
but only 9 LDCs are available

The following guidelines can help prevent creating a configuration that could overflow the LDC capabilities of the control domain:

1. The control domain allocates 12 LDCs for various communication purposes with the hypervisor, Fault Management Architecture (FMA), and the system controller (SC), independent of the number of other logical domains configured.

2. The control domain allocates 1 LDC to every logical domain, including itself, for control traffic.

3. Each virtual I/O service on the control domain consumes 1 LDC for every connected client of that service.

For example, consider a control domain and 8 additional logical domains. Each logical domain needs the following at a minimum:

• Virtual network

• Virtual disk

• Virtual console

Applying the above guidelines yields the following results (numbers in parentheses correspond to the preceding guideline number from which the value was derived):

12(1) + 9(2) + 8 x 3(3)=45 LDCs in total.

Now consider the case where there are 32 domains instead of 8, and each domain includes 3 virtual disks, 3 virtual networks, and a virtual console. Now the equation becomes:

12 + 33 + 32 x 7=269 LDCs in total.

Depending upon the number of supported LDCs of your platform, the Logical Domains Manager will either accept or reject the configurations.