One of the neat new (though understated) features of Lion is Whole Disk Encryption. Before I flick the switch, I'd love to know what the performance impacts (speed and battery impacts) of switching it on.

There are some great articles with qualitative data (see below - not to mention a good Ask Different Question), however it would be great to have some quantitative (or even anecdotal) stories of people who Filevault 2 has, or hasn't worked for.

What implications have you experienced in speed and battery life using Filevault 2?

Using FileVault 2: Performance impacts Once you have Filevault 2 enabled, you will not notice any performance changes. Whether it is real or a matter of perception, your files feel like they open just as fast. Your apps launch without any additional delay. Your backups via Time Machine work the same, etc. (themaclawyer.com)


All forms of whole disk encryption benefit from the current imbalance between CPU power and disk speed. In almost all circumstances, the CPU in your Mac spends most of its time twiddling its thumbs with nothing to do. This is especially true for operations that involve a lot of disk access.

Whole disk encryption takes advantage of this nearly omnipresent CPU cycle glut to sneak in the tiny chunks of work it requires to encrypt and decrypt data from the disk. Apple also leverages the special-purpose AES instructions and hardware on Intel's newest CPUs, further reducing the CPU overhead. The end result is that regular users will be hard-pressed to notice any reduction in performance with encryption enabled. Based on my experience with the feature in prerelease versions of Lion, I would strongly consider enabling it on any Mac laptop I plan to travel with. (Ars Technica)

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    I'll be amazed to see if anyone can actual perceive any difference, given the information in the second quote. Commented Jul 26, 2011 at 10:56
  • I'd forgotten that quote from John Siracusa's excellent review - thanks for jogging my memory. :)
    – Dan J
    Commented Oct 3, 2011 at 6:51
  • For those of you that are interested - I ended up using FV2 for about 2 months and turned it off because of poor performance (which I suspect is also a .0 and .1 set of bugs, along with my habit of running a lot of apps at the same time causing paging). I've got an old school spinning hdd rather than flash drive, which probably impacts the performance of fv2 as well.
    – glenstorey
    Commented Oct 4, 2011 at 3:11

2 Answers 2


Other than making sure you have power available when you turn on or off the entire disk's worth of IO to encrypt/decrypt, performance and power deltas are barely measurable.

Less than 1-2% is what I'm seeing. Other than hammering large IO benchmarks, in practice it doesn't matter one bit whether FileVault 2 is on or off for the initial build of Lion.

As long as you understand the limitations of not being able to use file recovery tools, how people can circumvent your encryption by losing control of pass phrases or keys, it seems this lunch is free (or at least on Apple's tab).

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    Thanks bmike - that's really helpful. I've not noticed any major slowdowns with file vault, now that it's turned on. The mobile backups can tie things up a bit on my i5. I don't know if this is a file vault thing, or just a throughput thing but it's negotiable for a .0 release.
    – glenstorey
    Commented Jul 30, 2011 at 23:50
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    negotiable = negligible? ;)
    – John
    Commented Jul 31, 2011 at 6:40
  • A useful comment about practice compared to large IO benchmarks. If you'd like to comment under, maybe edit this I'll be pleased: my answer under Apart from being able to encypt the entire drive, what are the other differences of Filevault 2 over Filevault?. Also FYI Speed of old Filevault vs. new Lion full disk encryption Commented Aug 4, 2011 at 15:10

I have a 2011 uMBP 15" i7 QC, 8GB RAM, with a OCZ Vertex 3 256GB SSD & Corsair F120. AFTER enabling FileVault 2, I did notice a throughput penalty (VERTEX 3) specifically, large file size write. Sequential reads showed 2-5% impact. Where write-throughput dropped >100MB/s. I owe the forum a more detailed comparison.

Regardless, having a secure volume with still-impressive throughput speeds is great.

I foresee the next few "iterations" of industry SSD products/benchmarks to include whole-disk encryption performance...an evolutionary competitive differentiator.

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