Release 2.0.6
A77230-01
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| Oracle Internet Directory Administrator's Guide Release 2.0.6 A77230-01 |
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This chapter discusses topics in the following sections:
Capacity planning is the process of assessing applications' directory access requirements and ensuring that the Oracle Internet Directory has adequate machine resources to service requests at an acceptable rate. Assuming that the Oracle Internet Directory and the corresponding Oracle8i database are running on the same machine, the following are the configurable resources that capacity planners need to consider:
When you plan to acquire hardware for Oracle Internet Directory, you should ensure that all components--such as CPU, memory, and I/O--are effectively used. Generally, good memory usage and a robust I/O subsystem are sufficient to keep the CPU busy.
Any new installation of the Oracle Internet Directory needs two things to be successful:
We begin by looking at an example of a directory deployment for an email messaging application in a hypothetical company called Acme Corporation. As we examine each component of the capacity plan, we will apply our recommendations to the example of Acme Corporation.
The ability to assess the potential load on Oracle Internet Directory is very important for getting an accurate capacity plan. Let us take a typical email messaging software in a big multinational company called Acme Corporation. The email messaging software is based on Internet Message Access Protocol (IMAP). There are two main types of software that access Oracle Internet Directory:
Let us assume that the private aliases and private distribution lists of individual users are also stored in the directory. Let us further make the following assumptions, which will allow us to guess the size of the directory:
Based on the above assumptions, we can derive the overall count of entries in Oracle Internet Directory as:
The above assumptions will yield a directory population of about one million entries. Given the user population and the directory population, let us then analyze usage patterns so that we can derive performance requirements from them. A typical user tends to send an average of 10 emails per day and receives an average of 10 emails a day from the outside world. Assuming that there are, on an average, five recipients for each email being sent by a user, this would result in five directory lookups for each email.
The following table summarizes all the possible directory lookups that can happen in one day:
Summing up, the total number of directory lookups per day would be about 3,200,000 (3.2 million) directory lookups per day. If these directory lookups were spread out uniformly along the day, it would require about 37 directory lookups per second (133,333 lookups per hour). Unfortunately, we will never have this case. Usage analysis of the current email system over a period of 24 hours shows the pattern illustrated in Figure 12-1.
The email system (and Oracle Internet Directory) is stressed at its peak in the mornings. There are other usage peaks as well--one close to lunch time, and one near the end of business day. But it is in the mornings that the Oracle Internet Directory is stressed the most.
Let us assume that 90% of all the directory lookups happen during normal working hours. Let us now split up the working hour load into the following categories (assuming an 8 hour workday):
The above calculations indicate that the Oracle Internet Directory in this case should be designed to handle the peak load of 936,000 lookups per hour.
Now that we know the data-set size as well as the performance requirements, we can now look into individual components of the installation and estimate good values for each.
The I/O subsystem can be compared to a pump that pumps data to the CPUs to enable them to execute workloads. The I/O subsystem is also responsible for data storage. The main components of an I/O subsystem are arrays of disk drives controlled by disk controllers.
It is important to consider performance requirements when you size the I/O subsystem, rather than size based only on storage requirements. Although disk drives have increased in size, the throughput--that is, the rate at which the disk drive pumps data--has not increased in proportion. In sizing calculations for the I/O subsystem, you should use the following factors as input:
Given a range of I/O subsystems, you should always opt for the highest throughput drives. Typically, one can maximize the I/O throughput by one or more of the following techniques:
Some guidelines for organizing Oracle Internet Directory-specific data files are provided in Chapter 13. Depending on the tolerance of disk failures, different levels of Redundant Arrays of Inexpensive Disks (RAID) can also be considered.
Assuming that the decision has been made to get the best possible I/O subsystem, we focus the rest of the section on deriving sizing estimates for the disks themselves.
Table 12-1 can be used to derive a rough estimate of the overall disk requirement:
| Number of Entries in DIT | Disk Requirements |
|---|---|
|
100,000 |
450MB to 650MB |
|
200,000 |
850MB to 1.5GB |
|
500,000 |
2.5GB to 3.5GB |
|
1,000,000 |
4.5GB to 6.5GB |
|
1,500,000 |
6.5GB to 10GB |
|
2,000,000 |
9GB to 13GB |
The data shown in Table 12-1 makes the following assumptions:
Going back to our example of Acme Corporation, since our directory population is about one million, this would imply that our disk requirements are approximately 4.5 GB to 6.5 GB. Note that the assumptions made for Acme Corporation regarding the number of cataloged attributes are different, but the table above should give an approximate figure of the size requirements.
Since the directory may be deployed for a wide variety of applications, these assumptions need not necessarily hold true for all possible situations: there might be cases where the size of attributes is large, the number of attributes per entry is large, extensive use of ACIs has been made or the number of cataloged attributes is very high. For such cases, we present simple arithmetic procedures in the following section which will allow the planners to get a more detailed perspective of their disk requirements.
Because Oracle Internet Directory stores all of its data in an Oracle 8i database, the sizing for disk space is primarily a sizing of the underlying database. Oracle Internet Directory stores its data in the following tablespaces:
In this section, we present simple arithmetic procedures to determine the size requirements of each of the tablespaces shown above. All of the size calculations will be based on the following variables:
Using the variables shown in Table 12-2, the size of individual tablespaces can be calculated as follows:
Using the arithmetic operations shown in Table 12-3, one can compute the exact space requirements for a wide variety of Oracle Internet Directory deployment scenarios. The sum of the sizes of each of the tablespaces should yield the overall database disk requirement. One can optionally multiply that by the "factor_of_safety" variable to get a figure that can compensate for unforeseen circumstances.
Going back to our example of Acme Corporation, we can assign values to each of the variables based on the requirements stated in previous sections. The following table illustrates the values of each variable introduced in this section for Acme Corporation.
If we now plug in these values into the equations described earlier, we get the following values:
The table above shows that the estimated size of the database for Acme Corporation would be about 6.9 GB. With a 50% factor of safety, this would jump to 10.4GB. If all of the data is being loaded in bulk, then the bulkloader tool of Oracle Internet Directory would require an additional 50% of space occupied by the database to store its temporary files. For Acme Corporation, this would add about 2.25 GB to 3.35 GB to the total space requirement.
Oracle Internet Directory is a database application. Memory is used for a number of distinct tasks by any database application. If memory resources are insufficient for any of these tasks, the bottleneck causes the CPUs to work at lower efficiency and system performance to drop. Furthermore, memory usage increases in proportion to the number of concurrent connections to the database and the number of concurrent users of the directory.
The memory available to processes comes from the virtual memory on the system, which is somewhat more than available physical memory. If the sum of all active memory usage exceeds the available physical memory on the system, the operating system may need to store some of the memory pages on disk. This is called paging. Paging can degrade performance if memory is too oversubscribed. Generally, you should not exceed 20% over-subscription of physical memory. If paging occurs, you need either to scale back memory usage by processes or to add more physical memory. Keep in mind the trade-offs: There are physical limits to the amount of memory you can add, but scaling back on per-process memory usage can significantly degrade performance.
The main consumer of memory is the database buffer cache within the System Global Area (SGA). The more memory allocated to this, the better will be the buffer cache hit ratio. A good buffer cache hit ratio will result in good database performance which in turn will result in good performance of the Oracle Internet Directory.
The following table gives minimum memory requirements for different directory configurations:
| Directory Type | Entry Count | Minimum Memory |
|---|---|---|
|
small |
less than 600,000 |
512MB |
|
medium |
600,000 to 2,000,000 |
1GB |
|
large |
greater than 2,000,000 |
2GB |
Going back to our example of Acme Corporation, the number of entries in the directory are close to 1,000,000 (1 million). We recommend choosing the 2GB option in order to maximize performance.
The network is rarely a bottleneck in most installations. However serious consideration must be given to it during the capacity planning stage. If the clients do not get adequate network bandwidth to send and receive messages from Oracle Internet Directory, the overall throughput will seem to be very low. For example, if we have configured Oracle Internet Directory to service 800 search operations per second, but the machine running the Oracle Directory Server is only accessible through a 10 Mbps network (10-Base-T switched ethernet), and we have only 60% of the bandwidth available, then the clients will only see a throughput of 600 search operations a second (assuming each search operation causes 1024 bytes to be transferred on the network). The following table shows the maximum possible throughput (in operations per second) for two types of operations (one requiring a transfer of 1024 bytes the other requiring a transfer of 2048 bytes) for two types of networks (10 Mbps & 100 Mbps) at different rates of bandwidth availability:
In some cases, it may also be important to consider the network latency of sending a message from a client to the Oracle Directory Server. In some WAN implementations, the network latencies may become as high as 500 milliseconds, which may cause the clients to time out for certain operations. In summary, given a range of networking options, the preferred choice should always be for highest bandwidth, lowest latency network.
Going back to the example of Acme Corporation, their peak usage rate is 936,000 lookups per hour which results in an equivalent number of lookup operations to the directory. This requires about 82 directory operations per second. Assuming that each operation results in a transfer of 2KB of data on the network, this would imply that we should have a 100 Mbps network or at least 60% bandwidth available on a 10 Mbps network. Since the 100 Mbps network will typically have a lower latency, we will chose that over the 10 Mbps network.
The CPU sizing for Oracle Internet Directory is directly a function of the user workload. The following factors will determine CPU configuration:
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 machine 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 (www.spec.org).
Since Oracle Internet Directory makes efficient use of multiple CPUs on an SMP machine, we chose to categorize machines 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 machine, whereas the baseline number represents the performance in normal circumstances.
Since Oracle Internet Directory is typically co-resident with the Oracle8i 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:
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:
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% CPU utilization. In this case, the CPU becomes the bottleneck.
Given this fact, we have taken the operation that consumes the smallest number of CPU cycles: a base search and estimated the number of concurrent operations at which we peaked on CPU usage on various machines. We then correlated this to SPECint_rate95 baseline number of the machines. With this correlation, given a certain amount of concurrency on the user load, one can find a lower bound on the processing power required by Oracle Internet Directory. The following formula gives the concurrency to SPECint_rate95 baseline number for this release of Oracle Internet Directory:
SPECint_rate95 baseline = 6.0 * (concurrent base search operations)
For example, if we need a machine that is capable of handling 50 concurrent base search operations before saturating the CPU, we would require a machine that has a SPECint_rate95 baseline rating of about 300.
Taking this number as the baseline, we can find the CPU requirements of other operations if we express them as some factor of the base search operations. The following factors may be used in addition to others:
Going back to our example of Acme Corporation, let us assume that we want adequate CPU resources to support about 100 concurrent operations. Assuming that each search returns 1.5 entries, and adding a factor of safety of 20%, our preliminary estimate of the CPU requirements would be:
SPECint_rate95 baseline=6.0*100*(1 + 0.2*1.5)*1.2 = 600*1.3*1.2 = 936
Looking at the available systems from the SPEC web site (www.spec.org) we can see that the following machine configurations would be the smallest configurations that should be considered. Table 12-4 shows some of the machines that Acme Corporation can consider for using for Oracle Internet Directory.
In the preceding sections, we have described various components involved in capacity planning and have also shown how each of them would apply to an Oracle Internet Directory deployment at a hypothetical company named Acme Corporation. In this section we give a quick summary of all of the recommendations made. Following were the initial assumptions:
Based on the above requirements and further assumptions, we developed the following recommendations:
Several simplifying assumptions were made so that the sizing calculations could be more intuitive.
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