AWS Migration Considerations: Pre-Cloud Migrations

AWS Migration Considerations: Part 1 (8 part series) Posted 31 March 2021

Welcome to the first article in our AWS Migration Considerations Series. You can find the start of the series here.

Digital system migrations have occurred since the dawn of digital services.

Every digital service that has endured for more than a couple of years has had a migration of some type. They are called many things, but servers, storage, and even data centres have been swapped out to new solutions over time.

A full data centre (to classical data centre) was often timed to be before the expiry of both existing IT equipment warranty expiry, and the lease expiry or renewal period. The process would start a year prior from the proposed end-date, with fresh equipment being reviewed and priced. Data centre visits would then be undertaken to inspect the new building and a standard set of mundane checks would be done:

  • I see no windows (there are none in most data centres)
  • I see N+1 Generators (reliable power supply)
  • and N+1 Automatic Transfer Switches (failover power supply)
  • and cabinets with raised floors for cooling
  • or hot-cold aisle configurations
  • and floor weight loadings
  • … just like our last facility, (but this one can support dual 15-amp power feeds).

And then a synchronised dance would happen:

  1. Order new data centre space with a nominated start date, around 2 - 3 months before the expiry of the old. $+
  2. Order the new hardware, with a delivery date just after the proposed start date of the new facility $+
  3. Modify DNS TTLs to a suitable low value (historically this was set to days or weeks)
  4. Wait until new equipment is delivered.
  5. Madly rack & stack, image systems, and extend networks to the new site
  6. Copy data – in one of several ways from old environment to new. (repeated rsyncs?)
  7. Downtime on the old facility, one more copy of data, and then update DNS to point to new IPs, and go live
  8. Decommission old systems. Un-rack, and return/sell. $-
  9. Give notice on the old facility. $-

You will note that we started paying for the new data centre, and the kit, well before the cut over. Even without a data centre change, there is the risk of doing something like a Storage Access Network (SAN) migration:

  1. Observe new SAN is coming to end of life or warranty renewal is becoming prohibitively expensive
  2. Determine new SAN equipment to move to (over weeks of research time)
  3. Determine there is not enough rack space in the current rack to install the replacement, so obtain an additional rack near the existing servers. $+
  4. Order new SAN. $+
  5. Wait for new SAN to be deployed
  6. Rack & stack new SAN
  7. Determine the data migration plan.
  8. Connect existing servers to new SAN (if there are enough fibre ports)
  9. Downtime on your services, move final data, remount file systems, restart service
  10. Disconnect servers from old SAN
  11. Dispose of old SAN.

All that work required resources. The cost of this as well as the cost of having new equipment while not yet using it, and old equipment that is no longer in use but not yet sold, represents a massive cost of operation.

You will find that because you have replaced a SAN it does not make people use your service or buy your product anymore; it is not a key differentiator in your market. We are doing this effort to maintain the technical environment.

These migrations within deployed solutions are continuous. Operating Systems, Hardware, Programming languages, Data Centres, Telcos & Internet Service Providers, DNS registries, CDN operators, database versions; the list is endless for the maintenance that is often overlooked or accumulating as Technical debt.


Modis has been an AWS Consulting Partner since 2013. You can learn more about our AWS Practice and services here.

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