The Australian Taxation Office has promised to conduct an independent review into a storage network crash it has labelled its "worst unplanned outage" in recent memory.
The ATO's online presence, as well as its internal Siebel and Sharepoint systems, went down on Monday following the collapse of an HPE storage network.
Data corruption issues from its primary HPE SAN were replicated onto its secondary SAN, leaving it scrambling to restore 1PB of storage capacity from back-up.
It brought its main website back online on Tuesday night, followed by its case management system the following morning, and its tax agent portal and business portal on Thursday.
It is currently working on stabilising its online services and has asked users to be patient with intermittent performance issues as it delivers full restoration.
ATO commissioner Chris Jordan today promised to task an independent reviewer with scrutinising what went wrong.
The expert will be asked to determine the nature of the failure, the root cause, the adequacy of back-up and contingency plans, and the likelihood of recurrence, he said.
Also under review will be the effectiveness of response by the ATO's vendor partners, including HPE.
"The review will also consider our immediate response to the failure, how we managed business resumption processes and the effectiveness of our communication with the community," Jordan said.
"I will be doing everything I can to learn from what has happened this week and to put in place any necessary changes to minimise the risk of any recurrence. Please be assured that I am committed to providing a quality, reliable and contemporary service to the Australian community."
He emphasised that the outage had not resulted in loss or compromise of data, and said it did not reflect on the ATO's overall IT capability or skills.
Jordan said all tax refunds that had been delayed as a result of the outage had been processed and would land in taxpayers' bank accounts either today or tomorrow.
"Any other refunds in the system will be fast-tracked to ensure people get these payments as quickly as possible - we have devoted additional resources to ensure the vast majority of people get their refunds on time," he said.
"We know the outages this week have caused inconvenience, especially so close to Christmas, and I apologise for that. I’d like to thank our clients, and in particular tax agents, for their patience and understanding."