Windows 2012 R2:

I am deciding on a RAID 1 (Mirroring in Windows terminology) implementation. I understand I have two options included in Windows:

  • Storage Space Mirroring
  • Disk Management Mirroring

How does Storage Space compare Mirroring to Disk Management Mirroring?


I have made some benchmarking on my home lab server using both technologies with two Samsung 850 PRO 512GB.

From what I can see, both mechanisms work the same way. Storage Spaces Mirroring performs better but consumes more CPU under diskspd benchmark, Dynamic Volumes Mirroring is a bit slower and obviously less CPU hungry.

Hope this helps you to decide what to go with.

  • Shame you didn't include any data; only reason I'm downvoting is that the other answer has some data. – StanTastic Jul 29 '20 at 14:03
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    @StanTastic - I think it's somewhat inappropriate to downvote one good, correct answer simply because another answer was better. The Help Center states that "voting down a post signals the opposite: that the post contains wrong information, is poorly researched, or fails to communicate information." serverfault.com/help/why-vote – Thomas Aug 17 '20 at 4:21
  • I beg to disagree - this post falls into "poorly researched" category, contains an opinion and only anegdotal data without any numbers. – StanTastic Aug 18 '20 at 7:08

I just wanted to ask the same question, after doing some tests of my own, here are my findings.

I am not using SSDs but rather standard HDs.

Using the disk managagement mirroring seems to be a little faster. I used queue depth of 8 and came up with values for blocksize 512B, 8KB, 64KB and 4M in Atto Benchmarking Tool:

10M/15M, 140M/155M, 202M/200M, 200M/201M plain disk, only 1 partition

9M/20M, 140M/200M, 200M/200M, 200M/395M plain mirror in disk management, only 1 partition

7M/12M, 133M/151M, 200M/204M, 201M/377M storage pool storage space on first partition, others are a little slower

But.. to me that is neglible, since real performance depends on random I/O (where performance is more similar) and also if you access/share the drives through 1GBit/s network, in which case there is a limit at a little over 100MB/s anyway.

Most important for mirroring is the (rare) error case. So I also googled how to restore a broken mirror. There seems to be a large difference - for whatever reason.

Recovery seems very complicated for storage pool/storage spaces mirror:


For disk management mirror it seems a lot easier


So: disk management way was slightly faster (for me, on Windows Server 2016), plus recovery looks a lot easier. I did not use any cache-size tweaking or anything similar.

I also did not compare CPU usage, since I assume that high CPU and high I/O won't go together very often.

Originally, I also wanted to compare Starwind Virtual SAN and mirror across servers (creating a cluster) but I guess local mirror with backups will be good enough and the performance comparison with that is useless due to network bottleneck.

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    +1 for downvoting and not leaving a comment after me taking a long time to write down results in a readable way – Andreas Reiff May 2 '17 at 15:18
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    I don't know who downvoted it. It supposed to be with a comment explains why. I am upvoting so it will be 0 :) – Allan Xu May 3 '17 at 0:05
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    I went through your answer and I appreciate the effort sharing your experiment result. Please note that SSDs are not a good representative of a benchmark due to their random access speed and their performance in general. – Allan Xu May 3 '17 at 0:14
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    Local mirror with backups saves you from disk failures and gives you an option to manually recover your server. Software like Starwind VSAN will save you in case when any of the components or even the whole server dies and is usually intended for an automatic failover (high availability). – Net Runner May 3 '17 at 20:20
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    I bought a QNAP storage and saved myself from dealing with windows disk manager. On my windows machines, I use a SMART monitoring/alerting tool. Most of mechanical disk failures are detectable through SMART codes a weeks before the disk dies. – Allan Xu May 4 '17 at 14:38

There is one big difference between "Disk Management" mirrored disks and "Storage Spaces". "Disk Management" is better from space utilization perspective, but not as flexible when physical storage needs to grow over time.

Assuming 2-disks are of the same size. Assuming "Disk Management" would use "Mirrored Mode" and "Storage Spaces" uses 2-way mirror.

Disk Management

PRO: Disk Management will simply duplicate your disk content to the 2nd disk and thus your total space available will be equal to the size of the drive. If you have 2 5TB drives, then you can store 5TB of data.

CON: When you are out of space you are out of space on the disk.

Storage Spaces

PRO: Storage Spaces allows you to allocate more space than currently physically available. When you are physically out of space, you can add 2 new drives of equal size to grow your pool. So, you can start with a couple 5TB and then add a couple 6TB drives and so on.

CON: You loose half of drive storage capacity in 2-way mirroring. If you have 2 5TB drives, then you can store 5TB/2=2.25 (and reduce that to lowest even number): 2.24 TB.

I don't know if Storage Space volume size can be increased after it is created without loss of data.

Data is based on my personal experience on Windows 10 Pro when I had to answer the same question.

  • In my case I went with "Disk Management" mirror due to desire to keep more disk space and higher performance mentioned above. – Sergei G Nov 15 '17 at 4:56
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    I disagree with your CON for Storage Spaces: "If you have 2 5TB drives, then you can store 5TB/2=2.25". I'm totally new to this, and didn't even know that Disk Management supported mirroring. But when I read about Storage Spaces, I created a Storage Space with 2 2TB drives two-way mirrored. As far as I can tell, the capacity of that Storage Space is 2 TB, not 1 TB as your statement would suggest. The "Properties" of the drive letter for the Storage Space shows capacity 1.80 TB with 1.08 TB used and 744 GB free. Is your CON a typo? – sootsnoot Jan 21 '19 at 5:53

Some additional information not yet mentioned in other answers:

Two reasons to use Storage Spaces over Mirrored Volumes via Disk Management:

  1. If you plan to use BitLocker for encryption, Mirrored Volumes does not support this but Storage Spaces does

  2. If you plan to use Backup and Restore (Windows 7) and you select a Mirrored Volume as the backup destination, you'll get a warning message along the lines of "When restoring a system image from this volume, the disks on your computer cannot be formatted to match the layout of the disks in the backup". This warning is not present when using a Storage Space as a backup destination.

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