Our MongoDB server had a few instances where it crashed after seeing the following log message,

{{

Unknown macro: {"t"}

,"s":"F", "c":"CONTROL", "id":4757800, "ctx":"conn455","msg":"Writing fatal message","attr":{"message":"DBException::toString(): LockTimeout: Unable to acquire IS lock on '

Unknown macro: {16140901064495857683}

' within 5ms.\nActual exception type: mongo::error_details::ExceptionForImpl<(mongo::ErrorCodes::Error)24, mongo::ExceptionForCat<(mongo::ErrorCategory)2> >\n"}}}}

 
I can understand that it causes writing to fail, but why would it be a fatal error? This can entirely be due to a transient hardware issues such as slow access to disk.