User guide

47MAXDATA SR1202 M1 – StorView
®
RAID User Guide
5. Choose the chunk size. Click the pull-down menu and select a chunk size (64K, 128K, or 256K).
For RAID level 0, 1, or 10 choose the correct size from the tables on this page. For RAID 5/50
applications, refer to the note below.
 NOTE
To achieve optimum RAID 5 write performance you should consider setting the chunk size based on
the specified number of drives for a Full Stripe Write when configuring RAID 5/50 arrays, for detailed
information see ”Optimizing RAID 5 Write Performance” beginning on page 141. You want to do as
many full stripe writes as possible.
 NOTE
The controller firmware will automatically set the chunk size if a smaller chunk size is selected than
the value recommended for the number of drives and specific RAID level.
RAID 0
Number of Drives
1 2 3 4+
Minimum Chunk
Size
256K 256K 128K 64K
RAID 1 & RAID 10 RAID 10 (0+1)
Number of Drives
2 4 6 8+
Minimum Chunk
Size
256K 256K 128K 64K
 NOTE
Chunk size is the amount of data that is written on a single drive before the controller moves to the
next drive in the stripe.
6. Select to Initialize the array. The default setting is to initialize.
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 based on the limit
of number of arrays, or 64.
 NOTE
The Trust Array option may be used in very special circumstances, see ”Trust an Array” beginning
on page 89.
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 (256 KB, 512 KB, 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 predetermined sizes to optimize the read performance based on
your data patterns.