The True Cost of Cold Storage

IT organizations today need to be savvy when it comes to spending budget. The shift of moving from on-premises storage to cloud-based storage is just one example of how organizations have delivered the same level of service, but at a reduced cost. That’s just good money management – always trying to get more bang for your buck. Providers of services like cloud backup are aware that businesses think this way – particularly when it comes to cloud storage.
Tiered storage offerings today are designed to align with business needs – from the most critical of data to the “let’s just keep in in case we need it someday”, and everything in between. These offerings have appeared to meet the specific need for cloud-based storage, but at a cost that lines up with value perceived of the data being stored.

So, is cold storage just cheap storage?

Cold Storage isn’t just about storage; it’s also about the service provided of saving data to, and retrieving data from cold storage. And when it comes to the cost of storage – especially storage intended to be used as part of a recovery effort – those service particulars become very important. Remember, for every less expensive storage option, there must be tradeoffs.

The Intangible Costs of Cold Storage

For some, the fact that cold storage is less costly (at least up front – more on this later) is all the information they need.  But, in reality, cold storage costs your organization more – both in tangible and intangible forms.

First the intangible:

  • It’s meant to be long-term – Any storage tier besides Hot storage tends to have some kind of storage minimum, along with a penalty cost, should you decide to remove the data sooner than the minimum. For example, Amazon Glacier has a minimum of 90 days of storage. Should you decide to remove the data prior to the 90 days, you pay for 90 days of storage anyway.
  • It’s slow – When you think of recovery, you’re wanting response times that parallel your organization’s sense of urgency – likely measured in minutes. But with cold storage, initial access and retrieval of data is generally available after a number of hours (e.g. Glacier’s standard retrieval is 3-5 hours to obtain the first bit).  Faster tiers of expedited retrieval are usually offered, but come at an additional cost that you won’t see until you’re under the gun to deliver a rapid recovery.
  • It can be less reliable – Even with data that you may not need for years (if at all) still needs to be accurate and uncorrupted.  Cold storage offerings usually have lower durability and availability service levels. While still touting several 9’s of service, this can have an impact on the organization’s ability to leverage any restored data, should it not be durable.

Calculating the Cost of Cold Storage

In addition to some of these less tangible costs that you may only experience should you have a recovery event, there are also very tangible costs that are incurred as a result of using cold storage – particularly during recovery. Assuming you’re considering Cold storage in order to save costs, let’s use an example scenario where you use Amazon for backup storage, and recover to an off-Amazon infrastructure. Let’s assume you have a 5TBs of data to initially be stored and then an additional 100GBs in changes monthly.

At the time of writing this article, standard storage pricing for S3 (for the first 50TB/month) is $.023/GB, with Glacier at only $.004/GB. So, storing the initial 5TBs and the monthly 100GBs over a period of a year in S3 costs a bit about $1500, whereas Glacier costs just under $400, as shown below.

Month S3 Only S3 + Glacier
S3 Storage S3 Cost S3 Storage S3 Cost Glacier Storage Glacier Cost Total
1 5,100 $117.30 5,100 $117.30 0 0 $117.30
2 5,200 $119.60 100 $2.30 5,100 $20.40 $22.70
3 5,300 $121.90 100 $2.30 5,200 $20.80 $23.10
4 5,400 $124.20 100 $2.30 5,300 $21.20 $23.50
5 5,500 $126.50 100 $2.30 5,400 $21.60 $23.90
6 5,600 $128.80 100 $2.30 5,500 $22.00 $24.30
7 5,700 $131.10 100 $2.30 5,600 $22.40 $24.70
8 5,800 $133.40 100 $2.30 5,700 $22.80 $25.10
9 5,900 $135.70 100 $2.30 5,800 $23.20 $25.50
10 6,000 $138.00 100 $2.30 5,900 $23.60 $25.90
11 6,100 $140.30 100 $2.30 6,000 $24.00 $26.30
12 6,200 $142.60 100 $2.30 6,100 $24.40 $26.70
Totals: $1,559.40 $142.60 $246.40 $389.00

Standard retrieval pricing for Glacier is only $.01/GB with a data access time of 3-5 hours. If you need it faster, “expedited” retrieval (of 1-5 minutes) is available at $.03/GB. At first glance, it seems far less expensive, when compared to the $.09/GB Amazon charges to transfer data from S3 out to the Internet. But, wait – you still need to pay an additional $.09/GB (the same as with S3) to transfer the data out of Amazon’s infrastructure to yours, making the total cost of retrieval higher than S3.

Assuming you need to recover the initial 5TBs and one incremental backup of 100GBs, the cost with S3 would be a little under $400, with the same recovery costing a bit over $600 with Glacier using expedited retrieval.

Determining Your True Cost of Cold Storage

There are a large number of storage, storage management, retrieval, and transfer options available that can materially modify the costs on either side. While there’s no argument that cold storage is definitely less expensive, it needs to be considered whether, for the hundreds of dollars less over the course of a year saved, your organization’s most critical data should rest on a storage platform that is designed to provide slower retrieval service, has lower durability and integrity, and costs the organization more in its’ time of need.