LaCie 131018 - StorView Snapshot - Mac, User Manual

Page: 60 / 214

StorView RAID Module
52
Initialization will begin automatically in the background once the array is created. You will have an option
to stop or pause the initialization from the Main screen. If you Stop an initialization, the array will be
trusted, see note below. As you create additional arrays, they too will begin initializing. The maximum
number of arrays that can be initialized in parallel is sixty-four (64).
Note The Trust Array option should only be used in very special circumstances, see 10.2.7 ”Trust an Array”
beginning on page 108.
7 Choose the “Back-off Percent” (reserved capacity) for the drives. The default is 1%.
This determines how much drive capacity to reserve for future capacity expansions or to enable
replacement drives of greater capacity sizes to be used.
Note The back-off percent option is not applicable to non-redundant array types. A RAID 0 array is a non-
redundant type of array and gains no benefit from establishing a reserve capacity.
8 Set the Read-Ahead Cache threshold.
The choices are automatic, disabled, and four pre-determined sizes (256KB, 512KB, 1 MB, and 2 MB).
Selecting Automatic, which is the recommended and default setting, allows the controller to determine
the optimum size. Selecting Disabled will turn off the Read-Ahead Cache. Select from one of the pre-
determined sizes to optimize the read performance based on your data patterns.
9 Set the Writeback Cache options.
Click the pull-down menu to select from Disabled, or choose one of the pre-determined cache threshold
sizes (1MB, 2MB, 4MB, 8MB, 16MB, 32MB, 64MB, 128MB, 256MB or MAX “MB”),
see 6.2.1 ”Configuring
Array Writeback Cache” beginning on page 54.
There are three additional options to an active Writeback Cache: Mirror Cache (Disable Writeback Cache
when partner controller fails or is missing), Disable Writeback Cache if a controller battery is low or fails,
and Disable Writeback Cache if array becomes critical (N/A for RAID 0), (e.g., during a rebuild). Enable
the options for your application. For maximum data protection, it is recommended to enable all three
options when applicable.
The Writeback Cache is used to optimize the write performance specific to your data patterns. In general,
larger cache sizes will increase the write performance but may lower simultaneous read performance.
The recommended size is 16 MB. The strategy of write operations results in a completion signal being
sent to the host operating system as soon as the cache receives the data to be written. The disk drives
will receive the data at a more appropriate time in order to increase controller performance.
10 Click the CREATE button to complete this process.
11 You will see a confirmation message that the array was successfully created, click the CLOSE button.
12 Click the CLOSE button at the bottom of the Create Array window.