Optimizing Disk Access

A critical component of deployment design is the speed of disk access to frequently accessed datasets, such as LDAP directories. Disk access provides the slowest access to data and is a likely source of a performance bottleneck.

One way to optimize disk access is to separate write operations from read operations. Not only are write operations more expensive than read operations, read operations (lookup operations for LDAP directories) typically occur with considerably more frequency than write operations (updates to data in LDAP directories).

Another way to optimize disk access is by dedicating disks to different types of I/O operations. For example, provide separate disk access for Directory Server logging operations, such as transaction logs and event logs, and LDAP read and write operations.

Also, consider implementing one or more instances of Directory Server dedicated to read and write operations and using replicated instances distributed to local servers for red and search access. Chaining and linking options are also available to optimize access to directory services.

Chapter 6, Tuning System Characteristics and Hardware Sizing, in Sun Java System Directory Server Enterprise Edition 6.0 Deployment Planning Guide discusses various factors in planning for disk access. Topics in this chapter include:

• Minimum memory and disk space requirements. Provides estimates for disk and memory needed for various sizes of directories.

• Sizing physical memory for cache access. Provides guidance on estimating cache size according to planned usage of Directory Server and on planning total memory usage.

• Sizing disk subsystems. Provides information on planning disk space requirements according to directory suffixes and Directory Server factors that affect disk use. and distributing files across disks, including various disk array alternatives.