Does scaling out bring TCO advantages over scaling up? The Reg offers advice

Provisioning

Today, this is still one of the most critical issues in all IT organisations. Once you have the resources in place, you have to provision them and, after some time, you realise you need more of them ... more than you have previously planned for maybe. (This is the exact moment you realise your forecast was off.)

It’s time to go back to the vendor and buy more kit for your infrastructure. In the case of scale-out it’s easy; you buy a new box and add it to the cluster. As I’ve already said, it’s likely to be a different, faster and higher capacity node type but it will work as expected.

However, things are totally different when it comes to scale-up systems.

You can buy a new tray of disks or add new ports, more cache and so on. Plenty of choice in theory ... but very few in practice. A traditional two-controller system has limited expandability and the chances are that the disks you need to expand your pool are out of production already. (How many times has that already happened to you? It's happened many times to me.)

At this point the vendor comes out with different options:

• Buy old disks at the cost of new ones
• Buy larger disks and use only a portion of them to maintain the system balanced and easy to configure/maintain
• Buy the same larger disks and start to mess with the configuration

This happens up to the limit of the controller, because then you’ll have to make a controller upgrade. (Argh! We'll come to this later.) At the end, a scale-out system is just much more manageable and has a longer longevity.

Migrations

Isn’t a migration the worst part of a sysadmin's life? And in large IT organisations this is almost a daily task. Even though things have vastly improved in the last few years, you always reach a point where a service disruption could happen (especially if you still have to deal with some physical servers and archaic OSs).

Scale-up systems, considering what I’ve already written about procurement and provisioning, are a pain in the neck when it’s time to update controllers or change the system backend. Compatibility matrixes, check lists, firmware upgrades and so on ... could make your migration activity a trip to hell (and sometimes it’s not a round trip).

But in any case, even though everything goes as smoothly as possible it’s the activity itself that is expensive and time consuming. For modern scale-out storage systems it is much easier and smoother to add a new node (just as you do when you want to expand the cluster), and in the worst case the cluster gets rebalanced.

When it's finished its job, you just decommission the node you no longer need. That’s all. It could take time, but it’s not your or anyone else’s time after all. And more importantly, it is always safer than a controller upgrade.

Closing the circle

Scale-out storage could cost more than scale-up when we talk about small systems but even in this case, TCO is the real parameter to look at when it comes to the whole life of the infrastructure and its sustainability.

In the particular case of POD-based deployments, adopting scale-out storage arrays is not an advantage for scalability but for the overall benefits it brings to daily operations, essentially by avoiding most of the limits and constraints of traditional scale-up systems.

If you want to know more about this topic, I’ll be presenting at next TECHunplugged conference in Austin, TX, on 02/02/16, a one-day event focused on cloud computing and IT infrastructure.

Disclaimer: Coho Data is a client of Juku Consulting