Reflect: max compression versus least compression?


Bob1212

Bob1212

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Can somebody kindly give me an idea of the mrimg size difference between the two? IOW, is it perhaps half?

My backup external drive is HDD, not SSD, so it'd take me more than a little while to run experiments. I'd just like a general idea.

Thanks.
 

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I would leave it at default. The higher the compression the longer it takes.
 

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1) No Compression - 8 mins, file size 37 GB (75 MB/S)

2) Medium Compression - 10 mins, file size 22 GB (35 MB/s)

3) High Compression - 16 mins, file size 21 GB
Click to expand...

Macrium Reflect and Compression - Windows 10 Help Forums

Did an interesting test on my OS drive which only contains OS and programs - no highly compressed data like videos. My drive contains 37 GB, and I got the following backing up to an hdd 1) No Compression - 8 mins, file size 37 GB (75 MB/S) 2) Medium Compr
www.tenforums.com www.tenforums.com
 

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TairikuOkami said:
1) No Compression - 8 mins, file size 37 GB (75 MB/S)

2) Medium Compression - 10 mins, file size 22 GB (35 MB/s)

3) High Compression - 16 mins, file size 21 GB
Click to expand...
Interesting. You only save 1GB between 2 & 3? If that's not a typo (and you say the same in your quoted link), then it seems hardly worth it.
 

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Porthos said:
I would leave it at default. The higher the compression the longer it takes.
Click to expand...
Well, since my destination drive is slow, I figured I just walk away and let it run anyway - until I get an SSD destination.
 

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Bob1212 said:
until I get an SSD destination.
Click to expand...
Note that compression will cause excessive writes. You will get 40GB image and then it gets compressed to 25GB, so it will write 65GB.
 

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TairikuOkami said:
Note that compression will cause excessive writes. You will get 40GB image and then it gets compressed to 25GB, so it will write 65GB.
Click to expand...
Ohhh... I would have guessed it compresses as it goes along.

So maybe an HDD destination is a more dependable choice in the long run.
 

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Will never again by a laptop without a backlit keyboard.
TairikuOkami said:
Note that compression will cause excessive writes. You will get 40GB image and then it gets compressed to 25GB, so it will write 65GB.
Click to expand...

Bob1212 said:
Ohhh... I would have guessed it compresses as it goes along.
Click to expand...
Bob1212 is correct, it compresses as it goes along. Only the compressed data gets written to the image file.

I have just repeated the tests that @cereberus did, and that TarikuOkami quoted above. My system has an SSD with a total of 26.51GB to back up to an external HDD. The findings were the same, but there's an added twist in the timings. Unlike cereberus I also included auto verify, so the verification time is included here:

High: image file 9.63GB in 7:06 minutes
Medium: image file 9.93GB in 5:33 minutes
None: image file 16.56GB in 6:26 minutes

As cereberus found, High compression gains very little at the expense of being significantly slower. But the real surprise was that Medium compression was the fastest of them all. Why? It's because verification reads every byte of the image just created, and the low compresiion image is some 6.6GB larger - it just takes more time to read it all.
 

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Bree said:
As cereberus found, High compression gains very little at the expense of being significantly slower.
Click to expand...

So high compression should be avoided, with possible exceptions such as a huge amount of .wav or .raw files, which are uncompressed.

...and maybe also if the source drive has a huge amount of empty space.
 

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Bob1212 said:
So high compression should be avoided,
Click to expand...
Yes, in general. There is very little to gain, and it's a lot slower.

I do use High compression myself, but only because I have a large number of machines to back up, and without it I would need a larger backup drive to hold all their images.

Bob1212 said:
...and maybe also if the source drive has a huge amount of empty space.
Click to expand...
No, Macrium's 'Intelligent sector copy' avoids including any empty space on the source drive in the image.
 

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    fully 'Windows 11 ready' laptop. Windows 10 C: partition migrated from my old unsupported 'main machine' then upgraded to 11. A test migration ran Insider builds for 2 months. When 11 was released on 5th October 2021 it was re-imaged back to 10 and was offered the upgrade in Windows Update on 20th October. Windows Update offered the 22H2 Feature Update on 20th September 2022. It got the 23H2 Feature Update on 4th November 2023 through Windows Update, 24H2 on 3rd October 2024 through Windows Update by setting the Target Release Version for 24H2, and 25H2 on 30th September 2025 through Windows Update by setting the Target Release Version for 25H2.

    UPDATE - 11 April 2026: due to mechanical deterioration this PC has been retired from active duty. The OS with all software and files has been migrated to my System Seven in 'Other systems' to carry on as my general purpose 'main machine'.

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    Windows 11 ProIntel® Core™ i5-520M8GB(integrated graphics) Intel HD Graphics
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    Intel® Core™ i5-520M
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    unsupported machine: Legacy bios, MBR, TPM 1.2, upgraded from W10 to W11 using W10/W11 hybrid install media workaround.

    In-place upgrade to 22H2 using ISO and a workaround.
    Feature Update to 23H2 by manually installing the Enablement Package.
    In-place upgrade to 24H2 using hybrid 23H2/24H2 install media.
    Upgraded to 25H2 by Enablement Package.

    Also running Insider Dev, and Canary builds and Windows 10 as native boot .vhdx.
  • My SYSTEM THREE is a Dell Latitude 5410, i7-10610U, 32GB RAM, 512GB NVMe ssd, supported device running Windows 11 Pro.

    My SYSTEM FOUR is a 2-in-1 convertible Lenovo Yoga 11e 20DA, Celeron N2930, 8GB RAM, 256GB ssd. Unsupported device: currently running Win10 Pro, plus Win11 Pro RTM and Insider Dev, Beta, and RP 24H2 as native boot vhdx.

    My SYSTEM FIVE is a Dell Latitude 3190 2-in-1, Pentium Silver N5030, 8GB RAM, 1TB NVMe ssd, supported device running Windows 11 Pro, plus Insider Beta, Dev, and Canary builds (and a few others) as a native boot .vhdx.

    My SYSTEM SIX is a Dell Latitude 5550, Core Ultra 7 165H, 64GB RAM, 1TB NVMe SSD, supported device, Windows 11 Pro 24H2, Hyper-V host machine. Updated to 25H2 on 30th September 2025.

    My SYSTEM SEVEN is a Lenovo Thinkpad T580, Intel Core i7-8650U, 16GB RAM, 512GB NVMe SSD + 2nd 512GB NVMe SSD, a supported device for Windows 11. This is my current general purpose 'main machine'. The installed Windows 11 Home from my System One has been migrated to this machine.
Similar experience by Ghost user

I am using Ghost backup. High compression will take longer time to finish. while save a little more size on disk. I do use High compression nearly every backup (unless disk to disk)
 

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