Understanding Azure Standard Storage and Pricing

[Image credit: mekuria getinet, https://www.flickr.com/photos/goma/]

Imagine that you’re brand new to Azure. You’ve been asked to price up a solution with some virtual machines. You use the best pricing tool for Azure and land at a page that has a bewildering collection of 12 items. You read through them, and are left none the wiser. I’m going to try cut through a lot of stuff to help you select the right storage for IaaS solutions such as VMs, backup, and DR.

There are a few things people expect when I present on storage in Azure. They expect LUNs with predefined sizes, they expect to see RAID, and when you talk about duplicate copies, they expect to see each copy. Sorry – it’s actually all much simpler than that – that’s a good thing!

Note that I will cover SSD-based Premium Storage in another post.

Terminology

You do not create LUNs in Azure; storage in Azure comes in units called a storage account. A storage account is an address point in the Azure cloud with 2 secure access keys (a primary key and an alternate secondary key to enable resetting the primary without loss of service).

When you create a storage account you create a unique URL. This could be used publicly … only if you know the very long secret access keys. You do not set a size; you simply store what you need and pay for what you store with up to 500 TB per storage account, and up to 100 storage accounts per subscription (by default). You also set a resiliency level to provide you with some level of protection against physical system failure.

Resiliency Levels

There are 4 resiliency levels, summarized nicely here:

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  • Locally Redundant Storage (LRS): 3 synchronously replicated copies are stored in a single facility in your region of choice. There is no facility fault tolerance. This is the cheapest resiliency level.
  • Geo-Redundant Storage (GRS): 3 synchronously replicated copies are stored in a single facility in your region of choice. 3 asynchronously replicated (no deprecation in performance) copies are stored in the neighbouring region, offering facility and region fault tolerance. This is the most expensive resiliency level.
  • Read-Access Geo-Redundant Storage (RA-GRS): synchronously replicated copies are stored in a single facility in your region of choice. 3 read only asynchronously replicated (no deprecation in performance) copies are stored in the neighbouring region, offering facility and region fault tolerance, but with read-only access in that other region.
  • Zone Redundant Storage (ZRS): Three copies of your data are stored across 2 to 3 facilities in one or two regions.

Note that we cannot use ZRS for IaaS (VMs, backup, DR). Typically we use LRS or GRS for VMs or backup storage. Azure Site Recovery (ASR) currently requires you to use GRS. You can switch between LRS, GRS and RA-GRS, but not from/to ZRS.

You do not see 3 or 6 copies of your data; this is abstracted from your view of the Azure fabric and you just see your storage account.

Here are the “neighbouring site” pairings:

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Azure Storage Services

Once you’ve figured out the resiliency levels, the next step in pricing is determining which storage service you will be using. There are four services:

  • Blob storage: In the IaaS world, we use this for Azure Backup. Files you upload are created as blobs. You can also use it to store documents, videos, pictures, and other unstructured text or binary data.
  • File storage: This is a newly available service that allows you to use an shared folder (no server required) to share data between applications using SMB 3.0. This is not to be used for user file sharing – use a VM or O365.
  • Page Blobs & disks: In the IaaS world this is where we store VM virtual hard disks (VHD) for running or replicated (ASR DR) VMs.
  • Tables & Queues: This offers NoSQL storage for unstructured and semi-structured data—ideal for web applications, address books, and other user data. Read that as .. for the devs.

This can be confusing. Do you need to create a blob storage account and a file storage account? What if you select the wrong one? It’s actually rather simple. When you upload a file to Azure it’s placed into blob storage in your storage account. When you create a VM, the disks are put into page blobs & disks automatically. If you start using file storage to share data between services via SMB 3.0, then that’s used automatically. And you can use a single storage account to use all 4 services if you want to – Azure just figures it out and bills you appropriately.

Storage Transactions

I am confused at the time of writing this post. Up until now, transactions (an indecipherable term) were a micro-payment billed at some tiny cost per 100,000. I had no idea what they were, but I know from my labs that the costs were insignificant unless you have a huge storage requirement. In fact, in my presentations I normally said:

The cost of estimating the cost of storage transactions is probably higher than the actual cost of the storage transactions.

And when writing this post, I found that storage transactions were no longer mentioned on the Azure storage pricing web page. Hmm! It would be great if that cost was folded into the price per GB – you can actually only do so much activity anyway because of how rack stamps are designed and performance is price-banded.

I’ve been told that people are still being billed, but no rate is publicly listed on the official site. I’ll update when I find out more.

Examples

Let’s say that I need to deploy a bunch of test Windows Server virtual machines that the business isn’t worried about losing. My goal is to keep costs down. I need 1000 GB of storage, accounting for the 127 GB C: drive, and any additional data disks. I know that this will use page blobs & disks, and I’m going to use LRS for this deployment. If I select North Europe as my region then the cost per GB is €0.0422 so the monthly cost will be around 42.2 – I say around because there will be some other small files maintained on storage.

I have a scenario where I need to replicate 5 TB of vSphere virtual machines to Azure using ASR. ASR requires GSR storage and I will be using page blobs & disks. The costs will be €0.0802/GB for the first 1024 GB and €0.0675/GB for the next 4096 GB. That’s €82.1248 + €276.48 = around €359 per month.

And what if will use 100 GB of storage for Azure Backup (DPM or direct). That’s going to be using blob storage, of either LRS or GRS. I’ll opt for GRS, which will cost €0.0405/GB, so I’ll pay a teeny €4.05 per month for backup storage (Azure Backup has an additional front-end per-instance charge).

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