Question: I'm upgrading my servers and I noted that Sun is offering their new "CMT" servers. I'm having trouble separating the hype from reality, and I'm not concerned about having a "green" machine room. What is the best way to objectively evaluate the Sun CMT servers for Oracle 11g?
Answer: At the lowest level a server is a server is a server, they are just processors with attached RAM. However, we are now seeing the hardware and OS community recognize that a typical database workload is I/O intensive (Suse Linux has an OS customized just for Oracle workloads), and they are introducing configurations that are designed specifically for a typical business workload, namely moving large volumes of data quickly.
But what makes the Sun CMT servers unique. The Sun docs note they the new CMT architecture considers real-world workloads:
"Sun's UltraSPARC processor engineering team has been obsessed with something entirely different: maximizing the throughput of real-world applications and workloads"
Sun CMT and the RAM speed issue
But there is a problem. CPU speeds have increased (and prices fallen), but this is not true for RAM, whose speed has remained relatively constant for decades (about 50 nanoseconds). As a result, the RAM becomes a bottleneck for the sever, and hardware manufacturers are addressing the issue by co-locating RAM very close to the CPU (such as the T1 RAM used with NUMA). See my notes on why "slow RAM
" plagues faster processing.
Sun CMT claims to have addressed this RAM bottleneck issue with a unique scheduling approach, using multithreaded chips that attempt to minimize waits for RAM buy starting new work when a processor is waiting on RAM. But what does this mean to the Oracle administrator? Let's take a closer look.
Oracle and Sun CMT
Sun has been a leader is server technologies and their announcement that they will deliver solid-state disk on all Sun servers in 2015
will revolutionize Oracle database administration. But the big question remains, "how does an Oracle DBA leverage on these new hardware architectures"?
In a nutshell, Oracle will use the resources that he needs, on demand, so the central issue will be the nature of your specific workload. As the 64-bit revolution led to large data buffer caches (and less disk I/O), Oracle system are often CPU-bound, and the application of more CPU's (or faster CPU) can relieve these conditions.
The Sun CMT approach is predicated on the idea that there will be additional processing work that can be done while waiting for RAM resources. However, a typical Oracle workload that moves data from storage to application programs is serial in nature, and the jury is still out as to whether the Sun CMT servers will have any dramatic advantage over their competitors.