Avago Technologies 3ware SAS 9750-16i4e - Manual (Page 123)

Setting Unit Policies
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6 Tab to the OK button and press Enter to select it.
You return to the main 3BM screen.
7 When you are finished making changes, press F8 to save them and exit
3BM.
Setting the StorSave Profile for a Unit
You can set the desired level of data protection versus performance for a unit
by selecting the StorSave Profile. Three profiles are provided: Protection
(maximum data protection), Performance (maximum performance, less data
protection), and Balanced (a middle ground). The default is Balanced.
About StorSave Profile Levels
The three profiles automatically adjust several different factors that affect
protection and performance on a per unit basis. These are summarized in the
table below and further explained after the table.
• FUA (Force Unit Access) . The FUA bit is a way that the RAID
controller or a program (such as a database program) can ensure that data
is actually written to the disk drive media, and is not stored in cache.
When a write command has the FUA bit set, then the disk drive will only
issue “command complete” to the controller once the data is written to
media. When performance is considered more important than protection,
it may be desirable to ignore the FUA bit.
Table 9: StorSave Profile Definitions
Protection Balanced (Default) Performance
Definition
Maximum data
protection, but slower
performance. More data protection than
Performance but less
data protection than
Protection. Maximum performance
for the unit, but less data
protection.
FUA (Force Unit
Access)
Honor FUA (If no BBU is
present)
Ignore FUA (If BBU is
present)
Honor FUA (If no BBU is
present)
Ignore FUA (If BBU is
present)
Ignore FUA
Write Journaling
Enabled Disabled, if no BBU
present. (Enabled, if BBU
is present.) Disabled (If BBU is
present, this essentially
disables the BBU for this
unit.)
Disable Cache on
Degrade Enabled Disabled Disabled