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What is an Inconsistent Unreadable Sector?

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Applies to

NetApp E-Series

Answer

Inconsistent Unreadable Sector

This record is a result of an inconsistent redundancy group discovered in the disk LBA associated with the record. When the inconsistency is discovered, records are created for every LBA in the sector-level stripe. These records are only created when the Pre-READ Redundancy Check feature is enabled.

If a sector is determined to be unreadable due to a physical media error OR an inconsistent redundancy group, the controller will not attempt to modify the contents of that disk sector.

For RAID levels other that RAID 6, and any RAID 6 redundancy consistency errors not corrected by additional RAID 6 processing, any cache blocks associated with the redundancy check will be invalidated, no data will be returned to the host, and the READ command will be completed with a CHECK CONDITION status and a SENSE KEY of MEDIUM ERROR (0x03) returned to the host. 

Reconstructing an Inconsistent Unreadable Sector

During disk reconstruction operations, INCONSISTENT Unreadable Sectors might be encountered, which map to the disk being reconstructed. Because the reconstruction is likely being performed for a new disk that has replaced a failed disk, there is no chance that the underlying data is accurate. In this situation, the INCONSISTENT sector that maps to the disk being reconstructed will be changed to a LOGICAL Unreadable Sector. An informational MEL event will be logged when this conversion takes place.

Clearing an Inconsistent Unreadable Sector

Clearing unreadable sectors causes the following to occur for INCONSISTENT errors:

  • Consistent redundancy data, based upon the existing user data, is generated for the stripe containing the unreadable sectors.
  • The unreadable sector entries are removed from the database

If an INCONSISTENT error that is being cleared maps to a drive that is currently failed, the underlying user data from the failed drive is not used to generate consistent redundancy information. In this case, a known data pattern will be used to represent the unreadable data that maps to the failed drive.

Additional Information

SANtricity OS 8.42+ introduces an additional data integrity feature for RAID 6 and Dynamic Disk Pools. During reconstruction operations, data consistency is checked. If a piece of data is found to be inconsistent and it cannot be corrected, all blocks in that RAID stripe are marked as INCONSISTENT in the unreadable sector log.

NetApp provides no representations or warranties regarding the accuracy or reliability or serviceability of any information or recommendations provided in this publication or with respect to any results that may be obtained by the use of the information or observance of any recommendations provided herein. The information in this document is distributed AS IS and the use of this information or the implementation of any recommendations or techniques herein is a customer's responsibility and depends on the customer's ability to evaluate and integrate them into the customer's operational environment. This document and the information contained herein may be used solely in connection with the NetApp products discussed in this document.