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Is it possible to encrypt entire hdd that already has data on it?

Topics: Users Discussion
Jan 29, 2016 at 9:38 AM
Im out of hdd space and i'd like to encrypt my hhds full of my data. Is it possible to encrypt hdds without destroying informations that exist on hdds?
Coordinator
Jan 29, 2016 at 9:55 AM
This is answered in the FAQ: https://veracrypt.codeplex.com/wikipage?title=FAQ#encrypt-in-place

During the process, read the warning messages carefully.
Jan 29, 2016 at 10:05 AM
Thank You, my english is poor so i was unsure what "in place" exactly means. Thank you for the answer, One more quick question. How long it takes to encrypt 1TB drive?
Coordinator
Jan 29, 2016 at 10:46 AM
The encryption time depends on two factors:
  • The read/write speed of your drive
  • The encryption algorithm used.
Usually, the limiting factor is the disk read/write speed not the encryption since we need to do both read and write for in-place encryption.

So, to have an idea of the time that will be taken, find the read/write speed of your drive, divide by two and this give you an estimation of the time needed.

For example, if your drive is connected through USB 2.0 (57 MB/s), this would give an theoretical in-place read+write speed of 57 = 28 MB/s. But in reality, USB 2.0 can be much slower than that, around 30 MB/s, which would give an in-place read+write speed of 15 MB/s. Thus, encrypting in-place the whole 1T drive would take at least (10^6 MB / 15 MB) seconds = 19 Hours. For such large data size, the encryption overhead is not negligible so it will take a little more than this (around 24 Hours)

Also, there is a step done before starting in-place encryption which is called "Shrinking": basically, we tell Windows to defragment the drive and put all the data at the beginning so that all data is contiguous.
This step is mandatory and unfortunately for disks with a large amount of data, "shrinking" can take a very long time! It is not possible to estimate the time taken by this because it depends on the fragmentation state of the data on the disk.

In all cases, when you start the encryption, VeraCrypt will tell the estimated time it will take. If you find it too long, you can just click "Defer" and then use the menu "Volumes -> Resume Interrupted Process" to decrypt what have been encrypted and get back your original clear content.
Jan 29, 2016 at 5:09 PM
I think VC does not tell that in-place encryption involves defrag, does it?!
Why is this used (and why is it mandatory) ?