AMCC 720-0138-00 manual Background Task Rate

Chapter 8. 3DM 2 Reference

Background Task Rate

The Background Task Rate fields let you change the balance of background tasks and I/O (reading and writing to disk) performed by the controller.

There are separate settings for Rebuild/Migrate Rate and Verify Rate, Figure 37. The Rebuild/Migrate Rate also applies to initialization. Although the same rate is used for rebuilding, migrating, and initializing, migrating has the highest priority.

The five radio buttons let you set the ratio at which background tasks are performed in comparison to I/O. For additional information, see “Setting Background Task Rate” on page 75.

Unit Policies

3DM lists each unit on the current controller, and shows you whether the policies are currently enabled or disabled for each unit.

Write Cache. When write cache is enabled, data is stored locally in memory on the drive before it is written to the disk drive media, allowing the computer to continue with its next task. This improves performance. However, in the event of a power failure, the data in the write cache will be lost if you do not have an uninterruptable power supply (UPS).

For additional information, see “Enabling and Disabling the Unit Write Cache” on page 45.

Auto Verify. When the Auto Verify policy is enabled, a verify task is performed automatically once every 24 hours. This feature is designed to make regular verification of units easier.

If a verify scheduling window has been set up and enabled, then Auto Verify will wait until the scheduled time window to start the automatic verify process.

When Auto Verify is not enabled, verify tasks are only run if you manually request one on the 3DM Management page. If a verify scheduling window is set and enabled, then manual verifies will wait until the scheduled time to start.

Continue on Source Error During Rebuild. This policy applies only to units which are redundant. (For units which are not redundant, a check box is not available.) When this policy is set, ECC errors are ignored when they are encountered during a rebuild. When this policy is not set, a rebuild will abort upon encountering an ECC error and the unit will be set back to Degraded.

Since this option could result in the loss of some source data in the event of source errors, select this option only if you want to ensure that a rebuild will complete successfully without manual intervention. If the rebuild fails and Continue on Source Error During Rebuild is not selected, then you have the

94 3ware Serial ATA RAID Controller User Guide for the Power Mac G5