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I got the new macbook pro 15' first two days batter life was really bad, 2 hours most. but on the 3rd day it went back to normal. now I get around 10 hours. I think it had something to do with Firevault. Encryption was running in the background and draining the battery now that it's done it's back to normal.

I think there is no need to freak out over this

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Encryption on a brand new Mac typically takes about an hour or so, unless you're dumping a whole load of data. I've always installed (via Homebrew Cask) a bunch of software on my new Macs and FileVault is caught up by the time it's done.

AES-NI - hardware encryption. There's no way FileVault should be taking that long unless you dump hundreds of gigs of data on at once.

To put some numbers on this, `cryptsetup benchmark` on my Linux notebook reports 1329 MiB/s encryption speed and 1346 MiB/s decryption speed for 256-bit AES in XTS mode (which is the default stream cipher for Linux's LUKS disk encryption). And that's on a 2012 Core i3.

If a modern CPU has AES-NI, I would never expect disk access speed to be constrained by the disk encryption. (Unless, maybe, if you're copying from one internal disk to the other, or if you're copying across a 10gig ethernet.)

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