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I would like to keep my 1.5TB USB 2.0 external drive that I use for backups encrypted. I'm using TrueCrypt and have created a fully encrypted volume. This took 18 hours.

My question is:

  • Does having the external drive encrypted slow down file transfer?

I know that it creates a little extra overhead for the processor (i5-2.5GHz-2core-64bitWin7-mem8GB). However, I would think that USB 2.0 would be the limiting factor anyways and in reality it would have little or no effect. If so, would switching to USB 3.0 move the bottleneck?

I'm willing to sacrifice speed for encryption. However, a large part of the backup is done with Crashplan+ which already does its own encryption (448bit). Of course there is no reason to double encrypt it like this, but for simplicity's sake I'd like to have the whole drive encrypted. However, if I could expect great speed benefits from having two partitions or keeping the already encrypted data from CrashPlan in the open, while placing the rest in a TrueCrypt container, then I might consider that.

I will do some tests myself and post the results as they come along.

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I found this post, maybe this will help answer your question a little. superuser.com/questions/366163/… –  JustinD Nov 27 '12 at 14:25
Thanks. I missed that one. The responses there indicate that with an internal drive, the bottleneck would be the drive and not the encryption. So for a USB drive 2.0 or 3.0, that transfer rate is always going to be the bottleneck and encryption should make little or no difference. –  Stoney Nov 27 '12 at 15:04

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