3Ware 9550SXU-12 User Guide - Page 237

Controller Settings page 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 103. 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 172. Unit Policies On the 3DM Controller Settings page you can enable or disable these policies: Write Cache, Auto-verify, Overwrite ECC, and Queuing You can also choose a StorSave Profile and change Rapid RAID Recovery settings. 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 controller's write cache will be lost if you do not have a battery backup unit (BBU) or an uninterruptable power supply (UPS). For additional information, see "Enabling and Disabling the Unit Write Cache" on page 118. Auto Verify. Enabling Auto Verify ensures that a verify takes place following either the Basic Auto Verify schedule or the Advanced Auto Verify schedule. For details, see "Enabling or Disabling Auto Verify for a Unit" on page 120. When Auto Verify is not enabled, verify tasks are only run if you manually request one on the 3DM Management page or in event of an unclean shutdown. Overwrite ECC (Continue on Source Error When Rebuilding). 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 Overwrite ECC is not selected, then you have the option to start a rebuild manually. It is recommended that you execute a file system check when the rebuild completes. Under Windows, you can do this by right-clicking on the www.3ware.com 225