CPU Requirements

This section contains these topics:

• CPU Configuration

• Rough Estimates of CPU Requirements

• Detailed Calculations of CPU Requirements

CPU Configuration

The CPU sizing for Oracle Internet Directory is directly a function of the user workload. The following factors will determine CPU configuration:

• The number of concurrent operations you want to support. This will be directly dependent on the number of users performing operations simultaneously.

• The acceptable latency of each operation. For example, in an e-mail application, a latency for each operation of 100 milliseconds might be desirable, but in most cases a latency of 500 milliseconds might still be acceptable.

CPU resources can be added to a system as the workload increases, but these additions seldom bring linear scalability to all operations since a lot of operations are not purely CPU bound. We classify the processing power of a computer by a performance characteristic that is commonly available from all vendors, namely, SPECint_rate95 baseline. This number is derived from a set of integer tests and is available from all system vendors as well as the SPEC Web site (http://www.spec.org).

Note: SPECint_rate95 should not be confused with the regular SPECint95 performance number. The SPECint95 performance number gives an idea of the integer processing power of a particular CPU (for systems with multiple CPUs, this number is typically normalized). The SPECint_rate95 gives the integer processing power of an entire system without any normalization.

Because Oracle Internet Directory makes efficient use of multiple CPUs on an SMP computer, we chose to categorize computers based on their SPECint_rate95 numbers. Even within SPECint_rate95 we chose the baseline number as opposed to the commonly advertised result. This is because the commonly advertised result is actually the peak performance of a computer, whereas the baseline number represents the performance in normal circumstances.

Rough Estimates of CPU Requirements

Since Oracle Internet Directory is typically co-resident with the Oracle9i database, we recommend at least a two-CPU system. We give the following rough estimates based on the level of usage of Oracle Internet Directory:

Table 20-13  Rough Estimates of CPU Requirements

Usage	Num CPUs	SPECint_rate95 baseline	System
Departmental	2	60 to 200	Compaq AlphaServer 8400 5/300 (300Mhz x 2)
Organization wide	4	200 to 350	IBM RS/6000 J50 (200MHz x 4)
Enterprise wide	4+	350+	Sun Ultra 450 (296 MHz x 4)

Detailed Calculations of CPU Requirements

It is difficult to determine the CPU requirements for all operations at a given deployment site since the amount of CPU consumed depends upon several factors, such as:

• The type operation: base search, subtree search, modify, add, and so on

• If SSL mode is enabled or not, since SSL consumes an additional 15 to 20 percent of CPU resources.

• If Oracle Internet Directory server entry cache is enabled or not, since the hit ratio affects CPU usage.

• The number of entries returned for a search

• The number of access control policies that need to be checked as part of a search

In most of the cases, except SSL, we can expect that there is a large latency between the Oracle Internet Directory server process and the database. When a thread in the Oracle Internet Directory server process is waiting for the database to respond, other threads within the Oracle Internet Directory server process can be put to work by other client requests needing LDAP server specific processing. As a result, for any mix of operations, one can always come up with a combination of concurrent clients and Oracle Internet Directory server processes that will result in 100 percent CPU utilization. In this case, the CPU becomes the bottleneck.

Given this fact, we have taken a 'messaging' type of subtree search operation and tried to estimate the CPU resources need to support a given number of concurrent operations without degrading the throughput of operations. The 'messaging' search operation involves subtree scope, a simple exact match filter and a result set of one entry. For Oracle Internet Directory 10g (9.0.4):

SPECint_rate95 baseline = 0.5 * (max # of concurrent operations at peak throughput)

This means that, if we need to support 600 concurrent clients without degrading the throughput of operations, then we need a computer that has at least a SPECint_rate95 baseline rating of (0.5 * 600) = 300.

In terms of throughput of operations, for Oracle Internet Directory 10g (9.0.4):

SPECint_rate95 baseline = 0.4 * (throughput of operations at max supported concurrency)

What this means is that if we need a throughput of 750 operations every second for the given maximum number of supported concurrent operations, then we need a computer that has at least a SPECint_rate95 baseline rating of (0.4 * 750) = 300.

It has been proven that Oracle Internet Directory scales very well with additional CPU resources. What this means is:

• For a given concurrency of operations, we can achieve higher throughput of operations (and hence, a lower latency) by adding additional CPU resources.

• For a given throughput of operations (and latency), we can support higher concurrency of operations by adding additional CPU resources.

Going back to our example of Acme Corporation, let us assume that we want adequate CPU resources to support 500 concurrent 'messaging' type of subtree search operations with each client seeing subsecond latency. Taking a factor of safety of 20 percent, our preliminary estimate of CPU requirement would be a computer with a SPECint_rate95 baseline of at least 360.