The following guidelines can help you determine the number of optical VPs to configure for your Optical Subsystem. The optimal number of optical VPs depends on the type of system usage.
Guideline One: The maximum number of optical VPs is equal to the number of clients performing optical I/O concurrently.
Guideline Two: However, if several clients are performing optical I/O concurrently, then use at least one optical VP per drive.
Scenario One: Clients are requesting writes on optical volumes in the same family. Multiple optical VPs for each drive allow additional clients to complete the initial setup while the first client is performing its I/O. The goal is to keep all the drives busy and maximize performance. If the optical objects are large, two optical VPs per drive are sufficient. If the optical objects are tiny (as in the case of signature verification), you need several optical VPs to keep the drives busy.
Scenario Two: Clients are requesting writes on the current optical volume in many different families. The write requests are randomly distributed across families. If the number of write requests is high, you would gain performance by having more optical VPs because you are more likely to get an I/O request for an already mounted platter before it is dismounted. Multiple optical VPs reduce the number of platter exchanges, a time-consuming operation.
Scenario Three: In a read-intensive environment, you should use one optical VP per optical drive.
Scenario Four: If the number of concurrent optical I/O request rates is low, a single optical VP for all optical drives might be adequate.
Home | [ Top of Page | Previous Page | Next Page | Contents | Index ]