Re: PSA: Windows shadow storage can silently consume all free disk space

Paul wrote:
> vssadmin list shadowstorage
> vssadmin 1.1 - Volume Shadow Copy Service administrative command-line tool
> (C) Copyright 2001-2013 Microsoft Corp.
> 
> Shadow Copy Storage association
>    For volume: (C:)\\?\Volume{0bd6166a-0836-4041-891c-792df2c72abd}\
>    Shadow Copy Storage volume: (C:)\\?\Volume{0bd6166a-0836-4041-891c-792df2c72abd}\
>    Used Shadow Copy Storage space: 0 bytes (0%)
>    Allocated Shadow Copy Storage space: 0 bytes (0%)
>    Maximum Shadow Copy Storage space: 2.37 GB (2%)    <===
> 
> Shadow Copy Storage association
>    For volume: (H:)\\?\Volume{bd4d69bc-6fbb-4f12-b804-f32c6b9e828c}\
>    Shadow Copy Storage volume: (H:)\\?\Volume{bd4d69bc-6fbb-4f12-b804-f32c6b9e828c}\
>    Used Shadow Copy Storage space: 29.8 MB (0%)
>    Allocated Shadow Copy Storage space: 320 MB (0%)
>    Maximum Shadow Copy Storage space: 6.45 GB (5%)    <===
> 
> I can see no contribution from File History to VSS, one way or another.

Hi Paul,

Wow. That was refreshing! It's exciting to learn from a Usenet response!

Thanks for posting your numbers as we can all work together as a well-honed
team given each of our setups have been modified over many years.

What you're showing above is actually the "normal" case, AFAICT, and it
helps confirm the point of the PSA for a properly set up Windows box.

Your C: drive has a maximum shadow storage size of 2.37 GB (about 2%).
Your H: drive has a maximum of 6.45 GB (about 5%).

Since VSS always reports the maximum shadow storage size as a percentage of
the drive it's associated with, not a percentage of used space, free space,
or anything else, your "2.37 GB (2%)" means, I think, that your C: drive is
roughly 118 GB in total size and your "6.45 GB (5%)" on H: means that H:
drive is roughly 129 GB in total size (AFAICT).

Both of those sets of numbers appear to me to be sane, bounded values. 
They likely won't run away and consume either of your entire disks.

In my case, the "Maximum Shadow Copy Storage space" was set to 100% of the
drive. I don't know why. I don't know how. I didn't even know to look.

Now I do know how to look, which is the main point of this helpful PSA:
 C:\> vssadmin list shadowstorage /for=C:

The output doesn't mean VSS was using what it reports, but only that
Windows was allowed to reserve that much if it wanted to. Once the disk got
tight, VSS and NTFS metadata allocation pushed right up against that limit
and the last few GB vanished instantly, while I was editing a text file.

Your output on a better-set-up PC shows the opposite situation than mine. 
Your max size is capped, so even if VSS wanted more space, it can't exceed
those limits on your machine so you won't likely see the same behavior.

Your additional helpful note about File History is apropos for this PSA.]

Looking it up, apparently Windows File History uses its own storage
mechanism & hence, it doesn't contribute to VSS usage. The two systems are
separate. I didn't realize it existed until you pointed it out. Thanks.
 Win+R > FileHistory 
 Reported: 
  a. No file history was found
  b. File History is currently turned off.
  c. Configure File History settings'
  d. Control Panel\All Control Panel Items\File History

It's probably important to note that it seems, after looking it up, that
File History does not use VSS shadow storage as it uses a normal folder
structure on whatever drive we selected as the File History target.
 <drive>:\FileHistory\<username>\<computername>\Data\
        
I'm not exactly sure what FileHistory is useful for, but it seems to be a
lightweight, automatic backup system for our personal files. 
 a. It's apparently not the whole system
 b. Nor the installed programs
 c. And certainly not the Windows installation itself
 d. But... it seems to know what is your "user data"

In fact, it seems to be kind of sort of a set of versioned copies of our
Documents, Pictures, Desktop, etc., stored on another drive. Is it?
  i. C:\Users\<you>\Documents
 ii. C:\Users\<you>\Pictures
iii. C:\Users\<you>\Desktop
 iv. C:\Users\<you>\Music
  v. C:\Users\<you>\Videos
 vi. C:\Users\<you>\Favorites
vii. C:\Users\<you>\AppData\Local\Microsoft\Windows\Libraries

I don't use the official folders in C:\Users so my data will all be stored
on C:\data\{my folder hierarchy that makes sense to me over the decades}
So FileHistory won't back them up unless I add those folders to a library.

Good to know.
Thanks for adding topical helpful value to this PSA about shadow copies.

It keeps older versions too, so we can apparently restore yesterday's copy
of a file we accidentally overwrote. It seems nice. If we have the space.

In addition to your helpful information about VSS and File History, 
that Acronis quote you found lines up with what I ran into. Some Windows
updates in the past (Creators Update era, Windows 8 era, etc.) were known
to reset the shadow storage maximum to very large values, sometimes 100%. 

If that happened years ago and nobody noticed, the system would run fine
until the disk finally got tight, and then the problem would appear
suddenly. Certainly my system dates to 2009 so it has had many updates.

So your numbers look good. Mine were simply misconfigured, probably from
something long ago. The PSA is just to help people check that setting in
case they hit the same failure mode.

Thanks again for the data point as it's wonderfully exciting to communicate
with people who want to add helpful value so as to benefit all who read it.
-- 
We're each here to learn and help others & to ask for help when needed.