Avago Technologies 3ware SAS 9750-16i4e - Manual (Page 124)

Chapter 7. Configuring Units
112 3ware SATA+SAS RAID Controller Card Software User Guide, Version 10.2
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 always enables write journaling and the
Performance profile always disables write journaling, regardless of the
presence of a BBU. The Balanced Profile disables write journaling if no
BBU is present, and enables write journaling if a 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, the write cache will automatically be re-enabled.
The Protection profile enables this feature, so that write cache is disabled
in the event a unit degrades; the Performance and Balanced profiles
disable this feature, so that write cache continues to be enabled.
Setting the StorSave Profile through 3DM2
In 3DM2, the StorSave Profile is a unit policy that can be set on the
Controller Settings page.
To set the StorSave profile through 3DM2
1 Choose Management >> Controller Settings from the menu bar in
3DM2.
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.