Pros & Cons of compressing the Operating System [Moved from News]

Another experiment.

I have just compressed my entire C drive. Originally I had around 43.8Gb free, then I tried the compressed binaries do-dah and free space increased as expected from 44.1Gb to 46.7Gb (at that moment in time). Now I've compressed the whole C drive and am up to 50.6Gb free (its a 70Gb partition).

Can I notice any difference?

I'm not sure tbh. I suspect some applications are opening faster than they did before. It was quick anyway with an SSD but the programs I've opened seem subjectively quicker. Opening in milliseconds. Have tried LTspice, Audacity, various Windows features such as notepad, paint and so on. All instant. Libre Office takes only a second or so. Web browsing is very snappy indeed.

I need to do a restart to be sure is good, and also do a back to see how that compares.

Edit... it took around 20 minutes to complete.

Edit edit… A full Disk Image (C drive) took around 1min 45secs. Transfer rate was a little higher at an indicated 170MB/s. Normally I see around 150-160MB/s for a full image and around 200MB/s when running incremental or differentials.
Edit edit edit… Next test will be the fastboot start. Typically around 16 seconds for 1809. That will be in a couple of hours probably.

Mooly said:

Another experiment. I have just compressed my entire C drive.Can I notice any difference? ... It was quick anyway with an SSD....

This is probably not an experiment you would want to try on an HDD. It would make very little difference for an SDD, but applying ntfs compression dramatically increases fragmentation...

Bree said:

As an experiment I have just copied 6GB of video files to an ntfs-formatted 8GB USB. As you'd expect, initially Defrag said 0% fragmentation. Then I applied ntfs compression to the whole drive, resulting in it being 24% fragmented.

Problem with audio and video files playback after ntfs folder decompre - Windows 10 Forums

Edit... it took around 20 minutes to complete.

It would take a lot longer than that to defragment an HDD after compression.

Bree said:

This is probably not an experiment you would want to try on an HDD. It would make very little difference for an SDD, but applying ntfs compression dramatically increases fragmentation...

It would take a lot longer than that to defragment an HDD after compression.

I hadn't considered fragmentation on a traditional drive... hmm.

I'd been wondering whether to try this on my ancient laptop (running W8.1) as the disc in/out rate is pretty abysmal. From what I read, compression can help if the drive is the weak link rather than CPU speed because reading a small compressed file is quicker than reading a non compressed longer file. A fast CPU makes the compressed system seem more responsive in that case.

I dunno I'll have to give it some thought, but one thing is probably certain, the old Acer would take all day to compress a drive that my i5 + SSD did in 20 minutes.

Oh yes, the fast start. All good with no discernible difference there. Shutdown was very rapid indeed at around 3 or 4 seconds.

New question (as you think of things.)

If you really wanted to run a compressed OS, when is the best time to apply the change? Would it be immediately following a clean install for example, and before you add any programs and files. In other words at the first possible opportuninty to do the compression. Or, would it be better to compress a fully finalised installation?

Any thoughts.

Mooly said:

I hadn't considered fragmentation on a traditional drive... hmm.
...New question (as you think of things.)
If you really wanted to run a compressed OS, when is the best time to apply the change? Would it be immediately following a clean install for example, and before you add any programs and files. In other words at the first possible opportuninty to do the compression. Or, would it be better to compress a fully finalised installation?

The 'first possible opportunity' actually occurs before you do the install. Setup has a command line option...

/CompactOS {Enable / Disable} Specifies whether to use the Compact OS feature to save hard drive space. By default, Windows Setup determines whether to use this feature automatically.

Windows Setup Command-Line Options | Microsoft Docs

Then marking the C: drive as using ntfs compression would ensure subsequent software you install would also be compressed. The ntfs compression only fragments an existing uncompressed file as you compress it. A new file copied to a compressed drive should not be fragmented.

Bree said:

The 'first possible opportunity' actually occurs before you do the install. Setup has a command line option...
Windows Setup Command-Line Options | Microsoft Docs

Then marking the C: drive as using ntfs compression would ensure subsequent software you install would also be compressed. The ntfs compression only fragments an existing uncompressed file as you compress it. A new file copied to a compressed drive should not be fragmented.

Thanks for all the info Bree, that's really helpful. I might amuse myself by reading up some more on all this.

I found my AOMEI full disk image comes out at exactly the same size as an image of the non compressed OS, presumably because AOMEI like other backup programs uses file compression and Windows has already done the work beforehand. Again, that's probably why the transfer rate was slightly higher for compressed vs non compressed.

Its both fun and informative trying all this stuff out

larc919 said:

I checked and CompactOS was invoked on my Fast Insider machine (120 GB SSD). I uncompacted it and checked again. It showed CompactOS was not invoked. But after I rebooted, it was invoked again.

I checked my c: (1809) and CompactOS (to my surprise) is also invoked. When I look at properties, there is a box to compress this drive. I am not trying it but just wondering.

meebers said:

I checked my c: (1809) and CompactOS (to my surprise) is also invoked. When I look at properties, there is a box to compress this drive. I am not trying it but just wondering.

Compressing the whole drive is exactly what I tried yesterday:

Windows 10 October 2018 Update rollout now paused

It been a very interesting experiment. Free space up from around 44Gb to 50Gb on a 70Gb partition. No obvious hit on performance that I could detect. I tried Edge, LibreOffice, Gimp, Audacity, Diptrace and LTspice and all opened in around the same time and seemed to take exactly the same time to perform their tasks, for example running a simulation in LTspice took 30 seconds for compressed and 30 for uncompressed.

After much deliberation I am however probably going to stick with non compressed. Why? I felt the system was 'calmer' in the long run and with less fan activity (laptop). Also, when I did a disk restore using AOMEI I got unexpected behaviour. The restore launched OK (from within the compressed OS) but following the reboot where the C drive is rebuilt I just got a blank screen. Normally I would see AOMEI's GUI together with a progress screen. Non of that appeared but as the HDD light was flashing away it seemed as though the restore was running. Sure enough, after 3 or 4 minutes the laptop booted into my restored Windows image as it should. The blank screen while the restore ran was something I'd never seen.

So on balance I'm back to all uncompressed and 6Gb worse off.

Mooly said:

Compressing the whole drive is exactly what I tried yesterday:

Windows 10 October 2018 Update rollout now paused

It been a very interesting experiment. Free space up from around 44Gb to 50Gb on a 70Gb partition. No obvious hit on performance that I could detect. I tried Edge, LibreOffice, Gimp, Audacity, Diptrace and LTspice and all opened in around the same time and seemed to take exactly the same time to perform their tasks, for example running a simulation in LTspice took 30 seconds for compressed and 30 for uncompressed.

After much deliberation I am however probably going to stick with non compressed. Why? I felt the system was 'calmer' in the long run and with less fan activity (laptop). Also, when I did a disk restore using AOMEI I got unexpected behaviour. The restore launched OK (from within the compressed OS) but following the reboot where the C drive is rebuilt I just got a blank screen. Normally I would see AOMEI's GUI together with a progress screen. Non of that appeared but as the HDD light was flashing away it seemed as though the restore was running. Sure enough, after 3 or 4 minutes the laptop booted into my restored Windows image as it should. The blank screen while the restore ran was something I'd never seen.

So on balance I'm back to all uncompressed and 6Gb worse off.

I am currently running uncompressed for all my systems UNLESS I am starving for free space (rarely these days). The main reasons for running uncompacted are:
A) Compatibility.
B) Better success of recovering data in case something goes wrong.
C) Partition backups compress better.
D) Uncompressed data can be accessed by other means outside w10 OS, in case you need it.

PS - We should create a separate thread for this. This is not the place to talk about compactos.

I'll see what John thinks over a separate thread for this. It is quite an interesting topic in its own right.