Understanding Azure VM Temp Storage Options and Considerations

Azure VM temp storage is a crucial aspect of running virtual machines in the cloud. It's essential to understand the different temp storage options available to ensure optimal performance and cost-effectiveness.

There are three primary temp storage options for Azure VMs: Azure Managed Disks, Azure Files, and the temp drive that comes with every VM. Azure Managed Disks offer high-performance, durable storage, while Azure Files provide a file share that can be accessed from multiple VMs.

Using the temp drive that comes with every VM is a convenient option, but it's not recommended for storing data long-term due to its ephemeral nature. This drive is designed for temporary storage, and data will be deleted when the VM is shut down or deleted.

Azure VMs also support the use of Azure Data Disks, which can be added to a VM to provide additional storage. Data Disks can be used for both temporary and permanent storage, and they offer better performance and durability than the temp drive.

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Azure VM Storage Options offer a variety of choices for your temporary storage needs.

Local SSDs provide the fastest storage option, with read and write speeds of up to 64,000 IOPS and 8,000 MB/s.

Temporary storage is ideal for applications that require high-speed storage, such as databases and caching.

Azure VMs can be configured with up to 4 temporary storage disks.

Premium SSDs offer a balance between cost and performance, with read and write speeds of up to 10,000 IOPS and 500 MB/s.

Standard HDDs are a cost-effective option, but have slower read and write speeds compared to SSDs.

Azure VMs can be configured with up to 16 temporary storage disks.

Curious to learn more? Check out: Azure Vm Cost

Azure offers several disk types to cater to different use cases and workloads.

Standard HDD (Hard Disk Drive) disks are suitable for low-priority and batch workloads, such as data archiving, data lakes, and big data analytics.

Premium SSD (Solid-State Drive) disks are ideal for high-performance and low-latency workloads, like databases, transactional applications, and gaming servers.

For another approach, see: Azure Vm Increase Disk Size

Ultra Disk is a high-performance, low-latency SSD disk type, designed for mission-critical and high-transactional workloads, such as online transactional processing, and real-time analytics.

Azure Managed Disks are block-level storage devices that can be attached to a VM, and are available in both standard and premium SSD types.

Azure Disk Storage can be used for both ephemeral and persistent storage, with ephemeral storage being ideal for temporary and stateless workloads, like web servers and containerized applications.

Curious to learn more? Check out: How to Attach Disk in Azure Vm

Azure VM temp storage is a temporary disk assigned to every VM, regardless of whether it's Linux or Windows. This disk is located on the physical server and is non-persistent.

The temporary disk is mounted as D:\ on Windows Server and as /dev/sdb1 on Linux-based VMs. The size of the temporary disk varies based on the size of the virtual machine and its available physical memory.

If you need to store data that must be persistent, avoid using the temporary disk altogether. This is because data from the temporary disk will not be preserved or moved to a new host in case of a host move, hardware failure, or other reasons. In fact, the disk is labeled as "Temporary Storage" and includes a warning text file to avoid misconfiguration.

Here's a quick rundown of scenarios where data from the temporary disk may be lost:

Azure Temp Drive for General Storage is not recommended for storing data. It's only temporary storage, so you risk losing data that can't be recovered if the virtual machine moves to a different host.

Data loss can occur due to various reasons such as resizing a virtual machine, updating the host, or a hardware failure on the host.

If you need to use the D: drive letter for an application, you can reassign drive letters so that the temporary disk uses something other than D:. For this, see Change the drive letter of the Windows temporary disk on MSDN.

Suggestion: Create Azure Data Lake Storage Gen2

Every Azure VM comes with a temporary disk, automatically assigned, which is located on the physical server where the VM is hosted and is non-persistent. This means that if your VM is moved to a new host, the data on the temporary disk will be lost.

The temporary disk is used for the operating system and additional data disks, which are stored in Azure Storage and are persistent. This temporary disk is labeled as "Temporary Storage" and includes a warning text file "DATALOSS_WARNING_README.txt" to remind you not to store important data on it.

For more insights, see: What Is Azure Storage

The size of the temporary disk varies based on the size of the virtual machine and its available physical memory. You can check the size of the temporary disk by looking at the "Temp storage (SSD) GiB" column in the Sizes for Windows virtual machines table.

There's no extra cost associated with the temporary storage provided with each Azure VM. This is a convenient feature, especially for storing temporary information or extending the physical memory.

The temporary disk is mounted as D:\ on Windows Server and as "/dev/sdb1" on Linux-based VMs. Be aware that storing data on the temporary disk can result in data loss, which cannot be recovered.

Here are some scenarios where data on the temporary disk will be lost:

For Windows Server, it's recommended to leave the pagefile.sys option system managed, as Microsoft recommends in KB 2860880. This is a valid practice, unless specified otherwise for a specific application.

Temporary disks in Azure VMs are non-persistent and located on the physical server, losing data when the VM is moved to a new host due to maintenance, hardware failures, or other reasons.

The temporary disk should never be used for data that needs to be persistent, as it can be lost in various situations, including resizing the VM, restarting it, moving to a new host, or updating the host.

Temporary disks in Azure VMs are automatically assigned and have a drive label "Temporary Storage" with a text file "DATALOSS_WARNING_README.txt" to avoid misconfiguration.

You can extend the physical memory to store information in case of a system crash, but it's recommended to leave the pagefile.sys option system managed, as recommended by Microsoft since Windows Server 2012.

Temporary disks come with no extra cost associated and their size varies based on the size of the virtual machine and its available physical memory.

Here are some reasons to avoid using temporary disks for general storage:

In Azure VMs, the temporary disk (D:) is used by default to store the pagefile.sys, which can cause problems if applications are installed on that drive.

This can be a challenge, especially in corporate environments where changing policies might not be a comfortable choice.

To remap the temporary disk to a different drive letter, follow the instructions in the article "Change the drive letter of the Windows temporary disk."

You can also extend the script to move the temporary disk during deployment using an ARM template, which is a common practice in modern deployments.

There's a project on GitHub called MoveAzureTempDrive that provides a great starting point for this task.

To use it, simply modify the azuredeploy.parameters.json file with the vmName and desired tempDriveLetter to be used.

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Tempdb is a great candidate for the temporary drive, but you need to consider a few things first. If you have an Azure VM instance, make sure you have enough space on the temporary drive - it can't be scaled infinitely.

Other workloads on the same VM might also be using the temporary drive, like Windows' pagefile.sys, which can compete for IOPS and storage space. This could be a problem if you're not careful.

To avoid issues, you should check if your monitoring solution will be affected by changing the way SQL Server starts up. This is an important consideration, so don't overlook it.

Azure VMs have a 1 TB temporary storage limit by default.

This limit can vary depending on the VM size and configuration.

Temporary storage is not backed up or persisted across reboots or VM shutdowns.

It's not suitable for storing critical data that needs to be retained.

Temporary storage is ideal for storing temporary files, logs, and other data that can be recreated or re-downloaded if needed.

You can increase the temporary storage limit by configuring the Azure VM's storage settings.

Some Azure VM sizes have a higher default temporary storage limit than others.

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