Disk subsystem

For I/O requests that must be satisfied from beyond the filesystem cache, there might be several improvements possible for the I/O subsystem. The storage subsystem containing the db.* files should have a memory cache; maximizing the storage subsystem’s memory cache is also a good recommendation. For best performance, write-back caching should be enabled, which of course requires that the storage subsystem’s memory have battery backup power. I/O latency to the logical drive where the db.\* files are located should be minimized, including the rotational latency of the physical drives themselves. Minimizing I/O latency might require direct connections between the host and the storage subsystem, and usually requires physical drives with the fastest rotational speed (such as 15K RPM).

RAID 1+0 (or RAID 10) is usually the better performing RAID configuration, and is recommended for the logical drive where the db.* files are located. The number of physical drives in the logical drive can also have an affect on *p4d* performance. Generally, performance improves as the number of physical drives in the logical drive increases. For a given amount of disk space required, better performance might result from using more smaller-capacity physical drives. The stripe size for the logical drive can also affect performance; the optimal stripe size might be dependent upon the number of physical drives in the logical drive.

Hardware-based RAID implementations (that is, RAID logic that is not implemented as software running on the host) usually have good performance characteristics. Software-based RAID implementations can require CPU cycles that might otherwise be needed for p4d processes. Therefore, software-based RAID implementations should be avoided.