LDoms is a new server virtualization and partitioning technology from Sun for CoolThreads systems. By deeply integrating the industry-leading multithreading capability of the UltraSPARC T1 processor and the Solaris 10 OS, the LDoms (or Logical Domains) technology allows you to allocate a system's various resources, such as memory, CPUs, and devices, into logical groupings and create multiple, discrete systems, each with their own operating system, resources, and identity within a single computer system.

Figure 19 depicts the architecture of a Solaris LDoms server.

Figure 19 : The architecture of a Solaris LDoms server

The hypervisor software/firmware of Figure 19 is responsible for maintaining separation (eg: visible hardware parts) between domains, and provides logical domain channels (LDCs) using which the domains communicate with each other. The control domain (see Figure 19) is the configuration platform for managing domains, and allows monitoring and reconfiguration of domains. The guest domains are where the applications are hosted, and can be independently powered on/off without affecting other domains. Note that Solaris LDoms support only Solaris and Linux guests.

As each of the guest domains can function like a full-blown operating system, this virtualization technology helps conserve space, reduce the physical size, and ease the management of large server-sprawls, typically characterized by hundreds of servers. How? Where ten physical hosts are required, a single Solaris LDoms server can now be used; ten guest domains can then be configured on the single Solaris LDoms server, with each guest playing host to a different operating system and a different application.

The applications on the logical domains use the virtual CPU/disk/memory resources that the hypervisor allocates to every guest. Typically, the hypervisor allocates subsets of the overall CPU, memory, and I/O resources of the server to a given logical domain. This implies that a resource contention at the host might impact the resource allocation to the guests, thereby affecting the performance of the applications executing on the guests. In a few other cases, the base Solaris host might be sized right, but the administrator might have improperly configured the size of a logical domain. A resource-intensive application executing on the domain would then leave a very high resource foot-print on the allocated resources, but would not affect the physical resource availability. Therefore, whenever an application executing on a domain experiences a slowdown, administrators might first need to determine where the root-cause of the problem lies – with the Solaris host or with the guest domain? To determine this, administrators need to continuously monitor the resource utilization of the Solaris operating system at the base, the control domain, and the logical domains on the Solaris server, so that they can proactively detect resource shortages or resource usage excesses, accurately indicate where the resource crunch has occurred, and help prevent adversities. This is where eG Enterprise helps administrator!