Azure makes it possible to store data on shared SSDs using the DS- and GS-Series virtual machines. This premium storage offers higher IOPS, lower latency, and better service performance for those services that truly require and are able to afford it. Azure Premium Storage is the kind of storage account that makes this possible. This post will explain what Azure Premium Storage can offer you.
Normally in Azure, we deploy virtual machines on standard storage, which is based on traditional spinning disks (HDDs). Depending on the machine type, you might get up to 300 IOPS (Basic A-Series) or up to 500 IOPS (all other virtual machines on standard storage) per data disk. If you require more IOPS, you can deploy more data disks and aggregate them to sum up their potential storage. But if you need more IOPS, and you require lower latency, then you should consider deploying Premium Storage, which is based on SSDs.
Once you have deployed a premium storage account, you can create DS- or GS-Series virtual machines that can use SSD data disks. Note that:
Normally when I talk about Premium Storage, I’m talking about data disks, but you can choose the DS-Series to deploy virtual machines with their OS disk on Premium Storage or Standard Storage.
There are two considerations:
The size of your premium storage data disk dictates the performance of the disk. You can deploy premium storage disks of any size, up to 1 TB, but the size is rounded up to determine the performance profile.
If you deployed a 50 GB data disk on premium storage, then it is rounded up to the P10 size and can achieve up to 500 IOPS with a throughput of 100 MB per second.
As with standard data disks, 1 TB is the maximum data disk size. You can exceed this size and aggregate performance by deploying multiple data disks in a virtual machine, and using features of the guest OS to stipe or mirror the data volumes.
A single premium storage account can scale up to 35 TB. If you need more than 35 TB, then deploy data disks from more than one premium storage account.
Look at the above table and pay attention to the throughput of each data disk size. A P10 can push 100 MB per second. Now look at the performance of the DS- and GS-Series virtual machines. Note how the DS-2 spec can only push data at 64 MB per second. That’s like putting a very fast SSD into an old laptop that cannot perform at the same rate as the flash storage.
There are a number of things to be aware of when considering premium storage:
You should not be considering Premium Storage for honest Sam’s Car Sales because they want a fast SQL Server. Premium Storage is expensive, so the decision to deploy a DS- or a GS- virtual machine with flash-based data disks should be the result of a calculation, and not based on how cold your finger is when you wet it and hold it in the wind.