You dont have javascript enabled! Please enable it! Step By Step: How To Extend And Resize A Two-Way Mirrored Storage Tiered Space? #StorageSpaces - CHARBEL NEMNOM - MVP | MCT | CCSP | CISM - Cloud & CyberSecurity

Step By Step: How To Extend and Resize A Two-Way Mirrored Storage Tiered Space? #StorageSpaces

2 Min. Read

Hello folks,

In the previous articles, I showed you step by step how to create a Two-Way mirrored Storage Space, and how to replace a failed disk and repair the storage space.

In today’s blog post, I will walk through how to extend and resize an existing Two-Way mirror Storage Space and volume.

First things first, we need to check the current status of the existing virtual disk before doing any changes.

Let’s open PowerShell and get the existing virtual disk information:


As you can see, we have a mirror storage space with 363GB SSD Tier and 2.2TB HDD Tier, but we don’t have any remaining space to extend the existing volume.


The current volume “D” has 2.53TB of disk space and 1TB of free size remaining.

In my demo, I will add 1TB to the HDD Tier, as a side note, the same will apply if you are resizing the SSD tier as well.

Now before we start increasing the pool capacity and resizing the virtual disk, you have to pay close attention to how many physical disks you can add to your existing storage space?

The answer to that question depends on what options were chosen when the virtual disk was initially created.

Let’s consider the following example:

You have a storage pool that has a 2-column, two-way mirror space. The two-column, two-way mirror space suggests you expand the pool capacity in sets of four disks for mirror spaces, in other words, you have to multiple the number of columns by the number of copies, and since we have 2 columns, we need at least four physical disks.

Another thing to remember is, that after adding disks to the pool, there is no rebalancing mechanism. So the existing disks will be filled up first before data is written to the added disks. That’s why the number of columns must be chosen carefully at the time you created a virtual disk because you can’t change the number of columns once the virtual disk is created.

With Get-VirtualDisk you can find many things about a virtual disk that you’ve created within a storage pool.


Since I am running a two-way mirror space with one column, I will add a 2 X 1TB HDD into my JBOD.


Next, we will add the newly added disks to the existing Storage Pool and then set the media type to HDD.



Let’s see the maximum capacity that we can add to the storage tier and extend the existing volume.


As you can see, we can add roughly 1.1TB.

Here is another important point to remember: When you are resizing the storage space, you have to specify the new total size, and not the amount you want to increase, so in my example above, the existing Storage Space for the HDD tier is 2,232GB, I need to add 1,116GB (new) + 2,232GB (existing) = 3,348GB total HDD tier, this of course if I need to add the whole capacity otherwise. The same concept will apply if you are resizing the SSD tier.

Let’s proceed and add the whole capacity.



Last but not least, we need to extend the existing partition which extends the volume “D” as well, and finally confirm the changes.




Microsoft has a great Storage Spaces Overview which goes into more detail and is well worth a read.

Hopefully, the above notes and screenshots illustrate how you can extend and resize a storage pool when you have a need to do so.

Until next time… Enjoy your day!


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About the Author
Charbel Nemnom
Charbel Nemnom is a Senior Cloud Architect with 21+ years of IT experience. As a Swiss Certified Information Security Manager (ISM), CCSP, CISM, Microsoft MVP, and MCT, he excels in optimizing mission-critical enterprise systems. His extensive practical knowledge spans complex system design, network architecture, business continuity, and cloud security, establishing him as an authoritative and trustworthy expert in the field. Charbel frequently writes about Cloud, Cybersecurity, and IT Certifications.

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1 thought on “Step By Step: How To Extend and Resize A Two-Way Mirrored Storage Tiered Space? #StorageSpaces”

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  1. Hi Charbel,
    awesome article. your explanations and pictures really paint a good picture. Thanks for sharing this information.

    I have a home LAB setup with Windows storage Spaces. planning on expanding the mirror by adding an External SAS storage enclosure.

    Thanks for the information again.

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