This white paper discusses various configuration scenarios and the corresponding workflows for setting up Sun Logical domains (LDoms) to deploy Veritas Storage Foundation for Oracle RAC (SFRAC). The scenarios in the white paper describe the deployment of SFRAC on LDoms in a single physical host as well as on multiple physical hosts.
Introduction to SUN LDoms
Logical Domains (LDoms) from SUN Microsystems is a technology that allocates resources such as processors, memory, disks or network devices to logical containers and manages them as logical domains within the physical host. The resulting LDom has its own operating system and manages resources independently in its realm.
Benefits of using SFRAC with LDoms
The LDom technology provides a very cost-effective alternative architecture for deploying SFRAC. The same physical server can be used for multiple applications within various logical domains with optimal resource utilization.
Best Practices for LDoms Setup
The following best practices are recommended for LDoms Setup.
On SUN platforms supporting LDoms, each CPU core supports four executing threads. These are represented as virtual CPUs on the system. Thus, a system with eight CPU cores would have 32 virtual CPUs. An LDom can operate with half a CPU core i.e 2 virtual CPUs, such being the case, a CPU core will be shared between LDoms. There are hardware resources that are allocated per CPU core basis and are shared between threads of that core. If threads are shared between LDoms, it can cause a performance degradation due to cache trashing. Hence, it is recommended to allocate a complete CPU core to an LDom rather that splitting it.
A domain having direct I/O access is recommended for database applications. Although database applications can run on virtual devices, there may be a slight performance degradation. Test deployments, where performance might be of lesser concern can use virtual disks for database applications.
Its strongly recommended to distribute LDoms on separate physical machines for clustered applications since it provides high availability in case of a physical hardware failure.
Note: For high Oracle workloads the minimum recommended configuration is 4 CPU/Cores and 8GB RAM.