[work in progress]
Overview - There are two ways to correct APEs.
1) Global catch all method. Failing two channels on the tier and do a rebuild, but this looses all RAID redundancies and leaves the RAID vulnerable if a third drive fails. (Typical RAID 6 setup)
2) Surgical method. Use 'cache noderebuild' to specifically repair a known LBA, this requires failing only one channel.
APEs are detected in two ways. 1) A result of tier or LUN verify within the S2A9900. 2) When a Fibre Channel client touches a block on the DDN which contains APE. They are distinguished by the presences or absence of a WWN entry in the log when the APE occurs. If a WWN is there then it is triggered by client side.
The 'faults' command shows a summary of all APEs if they exist. The counts are number of occurrences APE are detected and not the number of APEs contained within that tier/LUN, if the same APE is read 1000 times, then the count will show 1000.