3Ware 9550SX-4LP User Guide - Page 160

Chapter 8. Configuring Units The Protection and Balanced profiles honor FUA commands if no BBU is present; the Performance profile ignores them regardless of whether a BBU is present. If you use a battery backup unit (BBU), FUA is ignored, because the BBU preserves the contents of the controller cache memory for a limited period of time (up to 72 hours), in the event of a power failure. • Write Journaling. Write journaling tracks the writing of data to disk and preserves a copy of data that has not yet been written to the disk media. Following a power failure or in the event of accidental drive removal and reinsertion, the firmware can recover the unit without data loss. All pending writes sitting in the controller cache are replayed after power is restored or the drive is reinserted and are flushed from the controller to the drive. Using write journaling helps protect your data, however it can have an impact on performance. The Protection profile enables write journaling; the Performance Profile disables it. The Balanced profile disables it only if no BBU is present. If write journaling is disabled and a BBU is present, then it is as if the BBU was disabled for that unit. • Write cache disabled on degrade. In the event that a unit degrades, the use of write cache can be disabled until the unit is rebuilt. Once the unit is rebuilt, you must enable the write cache manually using 3DM2, 3BM, or the CLI. The write cache will not automatically reenable when the unit is rebuilt. The Protection profile enables this feature, so that write cache is disabled; the Performance and Balanced profiles disable this feature, so that write cache continues to be enabled. Setting the StorSave Profile through 3DM In 3DM, the StorSave Profile is a unit policy that can be set on the Controller Settings page. To set the StorSave profile through 3DM 1 Choose Management > Controller Settings from the menu bar in 3DM. 2 In the Unit Policies section of the Controller Settings Page, select the profile you want to use from the drop-down list in the StorSave column. The page refreshes, and a message at the top confirms the change you have made. 150 3ware Serial ATA RAID Controller User Guide