Chapter 8. Configuring Units150 3ware Serial ATA RAID Controller User GuideThe Protection and Balanced profiles honor FUA commands if no BBU ispresent; the Performance profile ignores them regardless of whether aBBU is present.If you use a battery backup unit (BBU), FUA is ignored, because the BBUpreserves the contents of the controller cache memory for a limited periodof time (up to 72 hours), in the event of a power failure.• Write Journaling. Write journaling tracks the writing of data to disk andpreserves 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 andreinsertion, the firmware can recover the unit without data loss. Allpending writes sitting in the controller cache are replayed after power isrestored or the drive is reinserted and are flushed from the controller tothe drive.Using write journaling helps protect your data, however it can have animpact on performance.The Protection profile enables write journaling; the Performance Profiledisables 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 theBBU was disabled for that unit.• Write cache disabled on degrade. In the event that a unit degrades, theuse of write cache can be disabled until the unit is rebuilt. Once the unit isrebuilt, you must enable the write cache manually using 3DM2, 3BM, orthe CLI. The write cache will not automatically reenable when the unit isrebuilt.The Protection profile enables this feature, so that write cache is disabled;the Performance and Balanced profiles disable this feature, so that writecache continues to be enabled.Setting the StorSave Profile through 3DMIn 3DM, the StorSave Profile is a unit policy that can be set on the ControllerSettings page.To set the StorSave profile through 3DM1 Choose Management > Controller Settings from the menu bar in 3DM.2 In the Unit Policies section of the Controller Settings Page, select theprofile 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 youhave made.
