Avago Technologies 3ware SAS 9750-16i4e - Manual (Page 161)

Background Tasks
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Background Initialization After Power Failure
The 3ware controller detects and handles power failures, using a mechanism
that ensures that redundant units have consistent data and parity. When a
redundant unit is unexpectedly shutdown, there is a possibility some data and
parity may be inconsistent. If a unit or sub-unit of a redundant unit is detected
to have been shutdown uncleanly, the unit or sub-unit will change its mode to
either ‘Initializing’ or ‘Verifying.’
When the initialization is complete, the unit is guaranteed to be redundant
again. The initialization does not erase user data.
This process will take less time if the unit is created with Rapid RAID
Recovery enabled during unit creation. See “Rapid RAID Recovery” on
page 113.
About Verification
The verify feature confirms the validity of redundant data on redundant units
and performs media scans on non-redundant units.
Regular weekly verification is a good idea, as it can provide early warning of
a disk drive problem or failure. This allows you to replace drives before they
fail.
You can start a verify manually or regular verification can be done
automatically by enabling Auto-Verify. (See “Starting a Verify Manually” on
page 152 and “Using Auto Verification” on page 152.)
During verification, I/O continues normally, but with a slight performance
loss, depending on your verify rate setting. You can adjust how much
verification will slow performance by setting a rate at which it occurs. (See
No RAID 5 with 3 or 4 disks
RAID 50 with 6, 8, or 9 disks
RAID 50 with 12 disks in 3 subunits of 4
RAID 50 with 12 disks in 4 subunits of 3
RAID 50 with 16 disks in 4 subunits of 4
Yes RAID 5 with 5 or more disks
RAID 6
RAID 50 with subunits of 5 or more disks
Table 12: Initialization Requirements for Different RAID
Configurations (continued)
Initialization Required for
Highest Performance?
RAID Configurations