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Data integrity codes are appended to the data being transferred at each component within the subsystem. The ECC/LRC (error correction) mechanisms ensures that fault does not cause the data to be changed without the user's knowledge. In addition to the ECC/LRC mechanisms all write data is mirrored in cache. For reference see chapter 3.3 of the Theory Of Operation Section.

Taken together these data protection mechanisms provide very strong safeguards against silent data corruption. Data loss/corruption is extremely unlikely to occur on SE9900 arrays. When problems do occur the SE9900 arrays have unparalleled ability to detect and recover from hardware and logic faults.

What does a pinned track mean 

There are several possible causes and recovery paths for pinned track scenarios, which are documented in chapter 4 of the Trouble Shooting Section of the SE9900 series Maintenance Manuals. One will need to identify which of the two error types have occurred in order to determine which data recovery procedure to use. There are two kinds of pinned track SIMs, which can be distinguished by the first three characters of the reference code in the SIM:

This article will focusing how to recover from FF4X-YY  Unable to process a track to or from Cache  type of pinned track for Solaris[TM] 7 or higher.

Certain types of transient or permanent hardware faults, and/or microcode bugs, may cause a mismatch between a cache slot's ECC/LRC data on either side of the mirrored cache. The customer data itself matches, or the array would not permit it to be read. Since the array has detected an ECC/LRC mismatch, it reports this error condition and "pins" the slot in cache, and the recovery method is left up to the customer.

The possibility of data corruption is very close to zero in these circumstances because data in both sides of cache matches.

Display and collect  Pinned Track  information

To display  Pinned Track  information refer to chapter 3.18 of the SVP Section of the SE9900 series Maintenance Manuals.

The [Detail] button will display the information whereas the [Archive] button will create an archive at c:\dkc200\others\pin\pin.lzh (SE9910, SE9960, SE9970, SE9980) or c:\dkc200\others\pin\pin.tgz (SE9985, SE9990) . This archive will be collected throughout an normal or detail autodump or downloaded individualy.

If the  Pinned Track  occurred on a LUSE volume (LUN Size expansion) the LDEV  reported in SIM and  Pinned Track  display might not match.  Pinned Track  display reports LDEV and PDEV within the LUSE.

The Recovery Procedure

Most of the time, the recovery procedures in chapter 4 of the Trouble Shooting Section are sufficient, and we should follow those recovery procedures first. Based upon the volume type used refer to the documented recovery flowcharts as below.

Recovery flowcharts

However the Erasing procedure which does not require the Pin Track Tool calls for a destructive format procedure to "recover" a pinned track under Solaris[TM]. In cases in which the pinned data still can be read from cache a non-destructive method will clear the pin with no data loss. File systems residing on the LDEV that has the pinned track will need to be unmounted, and the disk will need to be completely quiesced (i.e. nothing should attempt to access the disk while we are recovering).

Other than documented one will need to run format > analyze > refresh . This will read the data and then write it back.

Recovery flowcharts for Solaris which does not require the Pin Track Tool

In order to refresh an area of LBA one should convert the LBA  information provided by Pinned Track Display from hexadecimal into decimal. Based upon the emulation type calculate the stop LBA by adding number of blocks for one track. If you choose a size less than one track the Pinned Track might not be cleared.

Track size (cache slot size) to block translation

Glossary

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