CONFIGURATION PROCEDURES REQUIRED TO PROVIDE RAID-5 PROTECTION


CONFIGURATION PROCEDURES REQUIRED TO PROVIDE RAID-5 PROTECTION


For the IBM ServeRAID and ServeRAlD II Adapters, Synchronization and Initialization is required befbre installing an operating system or storing any customer data on a RAID-5 array for data integrity and to provide data protection. The RAID-5 arrays write data out to drives in stripe units. The size of the stripe unit can be configured to 8KB, l6KB, 32KB, or 64KB. Synchronization reads all the data bits in each stripe unit, calculates the parity for that data, compares the calculated parity with the existing parity for all stripe units in the array, and updates the existing parity if inconsistent. Initialization writes zeroes out to the logical drive. Operating systems may not install properly if the first few sectors are not set to zero (approximately the first 32 sectors).

After the user creates the array, he or she must create a logical drive. Logical drives are different from physical drives. Physical drives are the individual disk drives that are inside your machine. The logical drive is the drive that the array controller shows the operating system. A logical drive is spread across multiple physical drives. All RAID-5 logical drives must be synchronized after being defined before storing any data. The IBM ServeRAlD Configuration Utility does not force the user to synchronize the logical drive when defined in order to provide the customer the flexibility to define multiple logical drives and then synchronize them in one step. Once the array has been synchronized, the RAID-5 parity will remain synchronized until the logical drive is redefined.
If data is stored before synchronizing a RAID-5 array with the IBM ServeRAID and ServeRAlD II Adapters, this data is not protected: the corresponding parity for this data may not be correct. If you do not know whether the RAID-5 logical drives have ever been synchronized, then you can use the IBM ServeRAID SynchVerify/Update Diskette to determine whether the RAID-5 logical drives are synchronized or not. The SynchVerify/Update Diskette consists of the following two tools:

  1.  SYNCV1 - Synchronization Verification Utility
  2.  SYNCV2 - Synchronization Tool


The Synchronization Verification Utility is run during off peak hours to determine whether the logical drives are synchronized. If the RAID-5 logical drives are synchronized, no further action Is necessary. If the Synchronization Verification utility identifies that one or more RAID-5 logical drives may not be synchronized, then a full tape backup should be performed. Then, downtime must be scheduled to run the SYNCV2 tool to synchronize all the RAID-5 logical drives. Once the SynchVerify/Update Diskette has been run completely, the RAID-5 logical drives will remain synchronized until it is redefined.

The IBM ServeRAlD SynchVerify/Update Diskette is available at
http://www.us.pc.ibm.com/files.html.
Search for the filename with 'ServeRAID'.

If the RAID-5 logical drives have ever been synchronized, you do NOT need to run this IBM ServeRAID Synch Verify/Update Diskette.

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