HPE Smart Array P824i-p MR Gen10 User Manual page 18

• Higher performance than for RAID 6, especially during writes.
• Better fault tolerance than RAID 0, 5, 50, or 6.
• Up to 2n physical drives can fail (where n is the number of parity groups) without loss of data, as long
as no more than two failed drives are in the same parity group.
Parity groups
When you create a RAID 50 or RAID 60 configuration, you must also set the number of parity groups.
You can use any integer value greater than 1 for this setting, with the restriction that the total number of
physical drives in the array must be exactly divisible by the number of parity groups.
The maximum number of parity groups possible for a particular number of physical drives is the total
number of drives divided by the minimum number of drives necessary for that RAID level (three for RAID
50, four for RAID 60).
This feature has the following benefits:
• It supports RAID 50 and RAID 60.
• A higher number of parity groups increases fault tolerance.
Initialization state
Initialize a logical drive after you configure it. When you initialize the logical drive, you prepare the storage
medium for use.
CAUTION: All data on the logical drive is lost when you initialize it. Before you start this operation,
back up any data that you want to keep.
Fast initialization
During fast initialization, the firmware quickly overwrites the first and last 8 MB regions of the new logical
drive, clearing any boot records or partition information, and then completes the initialization in the
background. Monitor the progress of the initialization process using the progress indicator.
RAID levels that use parity (RAID 5, RAID 6, RAID 50, and RAID 60) require that the parity blocks be
initialized to valid values. Valid parity data is required to enable enhanced data protection through
background controller surface scan analysis and higher write performance (backed out write). After parity
initialization is complete, writes to a RAID 5 or RAID 6 logical drive are typically faster because the
controller does not read the entire stripe (regenerative write) to update the parity data. This feature
initializes parity blocks in the background while the logical drive is available for access by the operating
system. Parity initialization takes several hours to complete. The time it takes depends on the size of the
logical drive and the load on the controller. While the controller initializes the parity data in the
background, the logical drive has full fault tolerance.
This method has the benefit of allowing you to start writing data to the logical drive immediately.
Access the background initialization (BGI) rate by selecting Set Adjustable Task Rate under the More
Actions menu than locating it under the Priority Percentage column. Enter a number from 1 to 100. The
higher the number, the faster the initialization will occur (and the system I/O rate might be slower as a
result).
If you use RAID 5, you must have a minimum of five drives for a background initialization to start. If you
use RAID 6, you must have at least seven drives for a background initialization to start.
18 Features