3-9
Safety Information and Technical Specifications
4. Select Yes at the prompt and press Enter.
The CU displays a bar graph showing the initialization progress.
5. When initialization completes, press Esc to return to the previous menu.
If you press Esc while initialization is in progress, the Stop, Continue, and Abort
options are available, as explained earlier in this section.
3-3 Setting the Hard Disk Write Cache and Read Ahead
Policies
You can use the MegaRAID BIOS CU to set the hard disk drive Write Cache and
Read Ahead settings. Any read or write cache policy changes apply to all logical
drives on an array. In other words, if two logical drives are defined on a single array
and you change the Read Ahead setting on one logical drive, the change will also
apply to the other logical drive on the array.
The Disk Write Cache and Read Ahead policies can be set to On or Off.
• When the disk Write Cache is On, a write transaction is considered to be complete
when all the data has been written to the disk cache. When disk Write Cache
is Off, the write transaction is complete only when the data has been written to
the disk.
• When disk Read Ahead is On, extra data is read sequentially ahead of the data
that is actually requested and is stored in a cache. If the additional read-ahead
data is then requested, it can be read faster from the cache than from the disk
directly.
Note: When the disk Write Cache is On, there is a danger that data could be lost
if the power fails before the cached data is written to disk.
Follow these steps to view or change the logical drive Write Cache or Read
Ahead settings:
1. From the Management Menu, select Objects→ Logical Drive→Logical Drive n→
View/Update Parameters.
2. Use the arrow key to move the cursor to Disk WC or Read Ahead and press
Enter.
