AMCC 720-0138-00 manual About Verification, Background Initialization After Power Failure

Chapter 6. Maintaining Units

Initialization of RAID 1 and RAID 10 Units

RAID 1 and RAID 10 units do not need to be initialized when they are created to be fault tolerant and are immediately available for use with full performance when created.

Initialization of RAID 1, RAID 10 units will take place automatically the first time the unit is verified.

Initialization of a RAID 1 unit results in data from one disk (the disk on the lower port number) being copied to the other disk. In RAID 10 units, data from one half of the unit is copied to the other half.

After the initialization, subsequent verifies to a RAID 1 or 10 unit check for data consistency by comparing the data from one drive (or set of drives) to the other drive (or set of drives).

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.

About Verification

Verification can provide early warning of a disk drive problem or failure.This allows you to replace drives before they fail.

You can manually request a verify, or you can enable the Auto Verify policy, and the controller will automatically start verification once every 24 hours. (See “Starting a Verify Manually” on page 72 and “Setting Auto Verify for a Unit” on page 46.)

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 “Setting Background Task Rate” on page 75.) You can also postpone verification until a scheduled time. (See “Scheduling Background Tasks” on page 76.)

Note: Not verifying the unit periodically can lead to an unstable array unit and may cause data loss.

It is strongly recommended that you schedule a verify at least 1 time per week.

70 3ware Serial ATA RAID Controller User Guide for the Power Mac G5