Tip: Free-up hard drive space by decreasing space used by Shadow Copy Storage

Let’s start this article with a story. A little while ago, when I turned on my PC, I noticed one of my backup drives had significantly less free space than it should have (approximately 50 GB of space unused space was not available). I didn’t understand how this space was missing because I had not saved any data to the drive since the last time I had turned my PC off. I checked all the files I had on the drive. The storage space used by the files was about 50 GB less than the total used space being reported on my drive. I ran the scan disk tool in Windows to see if there were any errors on the drive, noting none. So where did this 50 GB mysteriously go? I was stumped. I ended up getting frustrated, backed up my data to a different drive, and reformatted the seemingly corrupted drive. After reformatting the drive, it was back to normal.

Fast forward into the future and something similar happened to me with another drive. This time I wasn’t about to flinch in the face of pure evil. Rather, I did some research and realized the “mysteriously disappearing space” is due to Shadow Copy Storage.

What Is Shadow Copy Storage?

Shadow Copy Storage is the place on your hard drives where shadow copies are stored by Volume Shadow Copy Service. Shadow copies may differ depending on the type of Windows you have but generally speaking, shadow copies are essentially System Restore points.

By default Windows sets aside 15% of total hard drive capacity or 30% of available free space for Shadow Copy Storage. You can check how much space is used by Shadow Copy Storage for your hard drives by:

  • Open Start Menu.
  • Run Command Prompt. (Be sure to right-click and Run as Administrator if you are on Windows Vista/Win7.)
  • Type vssadmin list shadowstorage…

…and hit Enter on your keyboard.

  • ¬†After you hit Enter, Command Prompt will show how much how much Shadow Copy Storage space is currently being used, the amount of total space allocated to Shadow Copy Storage, and the maximum amount that can be allocated to Shadow Copy Storage for each of your hard drives:

(Typically you’ll see 15% of hard drive is the maximum amount that can be allowed to Shadow Copy Storage but in my case it is 1% because I have already reduced it.)

Reducing Shadow Copy Storage

As mentioned above, by default Shadow Copy Storage typically uses 15% of total hard drive capacity. Simply deleting System Restore points does not recover this hard drive space. The only way to recover this space is to reduce the amount of space consumed by Shadow Copy Storage.

To reduce the amount of space used by Shadow Copy Storage on your hard drives, do the following:

Note: This guide is for Windows Vista and Win7. Windows XP users can easily reduce the amount of space given to System Restore by right-clicking on My Computer -> Properties -> System Restore -> selecting a drive -> Settings -> moving the slider.

  • Open Start Menu.
  • Run Command Prompt. Be sure to right-click and Run as Administrator.
  • In command prompt type vssadmin Resize ShadowStorage /For=[your hard disk]: /On=[your hard disk]: /MaxSize=[how much space you want to allocate] and hit Enter on your keyboard. For example, if I wanted to reduce Shadow Copy Storage on my E drive to a maximum of 9 GB, I’d type vssadmin Resize ShadowStorage /For=E: /On=E: /MaxSize=9GB:

Take note MaxSize can be in KB, MB, GB, TB, PB, or EB. Also note MaxSize should be set at 300MB or higher or else bad things will happen.

  • After you hit Enter, you should get a message saying successfully re-sized the shadow copy storage association:

Repeat this process for all the hard drives which you want Shadow Copy Storage to be reduced.

Food For Thought

dotTechies should be aware that there are drawbacks for resizing Shadow Copy Storage. The obvious drawback is if you set Shadow Copy Storage too low then System Restore – and whatever else is using Shadow Copy Storage – won’t function properly. Another drawback is resizing Shadow Copy Storage may cause your current System Restore points to be deleted.

Generally speaking, with hard drives being so large nowadays, it is not a good idea to modify Shadow Copy Storage space on your main drive. If you insist on modifying on your main drive, be sure to give it enough space for System Restore to function properly. I leave mine at 7% of total capacity.


If you ever find yourself in a sticky HDD storage situation, reducing Shadow Copy Storage may be a potential solution. Is it the best solution? I don’t know. Shadow Copy Storage has been reworked and made leaner in Windows 8 because, according to Microsoft, it has a “negative impact on performance” and is not used often. So maybe we are justified in reducing Shadow Copy Storage. Or maybe we aren’t. Who truly knows. Whatever the case may be, I’d suggest keeping this tip in mind if you are in urgent need of extra storage capacity.

[First image credit: TheBankBall]

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  • Arosh Wijepala

    I found a simple article explaining how to reduce the amount of space used by Shadow Storage via command prompt.


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  • Wow! This shadow copy storage si really cool! I experienced similar situation with my pc just the other day. I didn’t know about this shadow copy storage then. Thanks for the information in this article! This would be a great help for me.

  • Because I’m not familiar with this Shadow Cloud, in order for me to clear some hard drive storage, I just delete the unnecessary files :-) It’s a safe thing to do for me, though.

  • tejas

    @Frank D: +1 on that. System restore has helped me much more often, than it has failed me.

  • Frank D

    There was a period of about a week, just over a week ago, where I used System Restore — successfully — day after day because of a disk problem I was hunting down and finally fixed. If I hadn’t had access to System Restore for all those days, I would not have been able to boot or run my computer into a workable state so I could find and fix the problem. I’m a dedicated user of System Restore.

  • Janetb

    Since I moved to Win 7, my System Restore points were not being done automatically, as they were in XP, and they OFTEN disappeared altogether. I saw from forums that disappearing Sys Rest points were a common problem with Win 7. When I started doing proper backups, I closed Shadow Copy Service (ie System Restore) completely.

  • Jyo

    “Note: This guide is for Windows Vista and Win7. Windows XP users can easily reduce the amount of space given to System Restore by right-clicking on My Computer -> Properties -> System Restore -> selecting a drive -> Settings -> moving the slider.”

    You can access this “slider” in Windows 7 too. Right-click My Computer -> Properties ->System Protection -> Configure -> Max Usage Slider. I also do this to reduce the amount of space used by system restore to 2%. But I don’t think this slider configures multiple drives, so your command line method is still handy for that.

  • Johann


    +1 on that mate

    I use my lappie at work and home. i use GBM backup manager, mirroring as from 07:05 every 3.5 hours. This schedule means that it runs when I am not in office and tereis no resource impact to be felt. Do a Disaster backup when I feel I have too mamy of Ashraf’s freebie installs. System restore is totally stopped.

    Thx for the article Jeremy

    Used to use Paragon and Synctoy for the same type of setup, don’t get me wrong, it was an excellent setup and worked great. Now I only use one program instead of two.

  • Jeremy

    I agree with Frank D and KMHamm as far as it being a last resort. In my situation, I only performed this trick on my backup drives where I wouldn’t need a restore point if something went wrong. As stated in the article, I would not use this on my main OS drive. Like Phil and Ashraf stated, I am not a fan of System Restore either. Sometimes it works, other times it doesn’t. In my case on my 1 Terabyte backup drive, Shadow Copies was taking up 110GB of storage capacity, while on my smaller backup drive that is only 250GB it took up about 50GB. I personally don’t see a point in having a back-up for a back-up so-to-speak. You can choose how much space you want to allocate for shadow copies so you do not need to eliminate them completely. Personally, I don’t need 5 or more restore points sitting there taking up space. 2 or 3 is fine for me. But if I find I have to go back 2 or 3 restore points to fix a problem that has just occurred, it always seems to cause problems and not work the way it should.

  • Ashraf

    @Frank D and @KMHamm: I agree that this should only a last resort, if a resort at all, when trying to recover HDD space.

    @Phil: While System Restore has improved since XP, I don’t much like System Restore either… It is like a hit or a miss, and I don’t want that type of reliability when my computer has crashed.

  • Phil

    Personally I prefer to rely on a weekly image back up and store said images on a different Hard Drive. System Restore is one of the first things I turn off when doing a fresh install. Its not like if things go pear shaped it will set things back as they were depending on the severity of the problem. Still at the end of the day I guess what ever works for you.
    Glad I’m still using XP

  • This is one of the last things I’d do to reclaim space. I’d clear duplicates, then burn off the media files way before this kind of tweak. True especially if you have no idea what to do or the possible downside (and don’t have a geek pal handy if you mess it up). Hey – and going out to buy a new hard drive is fun!

  • Frank D

    IMO: This is one of the cases where “you can” do something you think is desirable to the system’s defaults, but where the answer to the question of “should you” is unknown. Who can know that doing something desirable from one aspect will or will not cause something undesirable to happen down the line, for which no cause can be determined? I would rather not tweak the system’s defaults without a documented “handle” that has been provided by the designer in the GUI. I know, it’s a bit like saying don’t go there because “if man were intended to fly he would have been given wings,” but in the past I have regrettably indulged in arcane tweaks that have had unintended consequences, which could only be undone by doing a system restore or, worse, a full image restore. My instinct is to play it safe and “if it ain’t broke, don’t try to fix it.”

    Frank D