EMS log reports "event extCache.io.writeError" in systems with Flash Cache card

Applies to

FAS platforms with a Flash Cache card 

Issue

• EMS log reports the event "wafl_exempt02: extCache.io.writeError", which is available by the event log show -severity notice command. Example:

[node_name: wafl_exempt00: ems.engine.suppressed:debug]: Event 'extCache.io.writeError' suppressed 114 times in last 110068 seconds.
[node_name: wafl_exempt00: extCache.io.writeError:notice]: WAFL external cache I/O write error: Insertq_save: unable to set up context chain, code 0. 
 

• Flash Cache NVMe state is OK.

::> system node run -node node_name -command sysconfig -a
    ...
    slot 3: Flash Cache NVMe
        Serial Number:      S123NE4W456789
        Part Number:        119-00329
        Hardware Revision:  D0
        Firmware Version:   NA01
        Firmware File:      X3311_S000PM9A3NVM
        Model Name:         X3311A
        Capacity:           1024 GB
        State:              ok

• No evicts and correct disk_reads_replaced counters. Example:

::*> statistics catalog counter show -object ext_cache_obj [advanced mode command]
...
start        end          instance  inserts (/s)  total_ops (/s)  hit (/s)  evicts (/s)  disk_reads_replaced (/s)
... 03:04:05 ... 03:09:05 ec0             882.70          126.47   1273.07         0.00                    112.69
... 03:14:05 ... 03:19:05 ec0             755.35          143.95   1381.05         0.00                    132.14
... 03:24:05 ... 03:29:05 ec0             938.33          200.68   1726.44         0.00                    186.02
...

• All data aggregates are full SSDs or hybrids
• External-cache module enabled. Example:

::> system node external-cache show -node node_name
Node: node_name
            Is Enabled: true
                    ...
Is hya caching enabled: true