Tuesday, 30 December 2014

Enabling FileVault on Yosemite

Read the full details here before doing anything: http://support.apple.com/kb/PH18637?viewlocale=en_US

Enabling disk encryption on OSX Yosemite turns out to be a straightforward process. Simply enable it through Setting/Security & Privacy/FileVault - if you chose not to let your iCloud account unlock your disk (for when you've forgotten your password) you'll have to keep a safe record of the recovery key (it sounds like you only get one oppourtunity to record this) - this triggers a reboot, and then when you log back in you'll be able to monitor the progress of file encryption from the same settings panel.

I have 2 MacBooks:

  • July 2014 Apple MacBook Pro, 2.6GHz Quad-core Intel Core i7, Turbo Boost up to 3.8GHz, 16GB 1600MHz DDR3L SDRAM, 512GB PCIe-based Flash Storage
  • January 2011 Apple MacBook Air, 13 inch display, Core 2 Duo 1.86GHz, 4 Gig RAM 1067 MHz DDR3, 256 Gig SSD
Since disk speed is king, I wanted to measure the effect of enabling FileVault so I found this benchmark script to hopefully capture a meaningful before and after state: http://www.amsys.co.uk/2013/blog/using-command-line-to-benchmark-disks/#.VKDxQsAGA

Unfortunately the purge command now needs to be run as sudo - before I enabled FileVault I ran it without sudo so I didn't get accurate read results. I hope though that the write values are accurate - I did multiple runs just to capture a feel for the variability:

Before FileVault (without sudo purge, read results were invalid)

MacBook Air:
  • Write Speed is: 211.474 MB/sec
  • Write Speed is: 211.479 MB/sec
MacBook Pro:
  • Write Speed is: 749.875 MB/sec
  • Write Speed is: 747.208 MB/sec

After FileVault (with sudo purge, read results look reasonable)

MacBook Air:
  • Read Speed is: 177.373 MB/sec
  • Read Speed is: 179.464 MB/sec
  • Write Speed is: 162.953 MB/sec
  • Write Speed is: 162.258 MB/sec 
MacBook Pro:
  • Read Speed is: 764.053 MB/sec
  • Read Speed is: 762.525 MB/sec
  • Write Speed is: 665.999 MB/sec
  • Write Speed is: 692.193 MB/sec
IF this benchmark is valid, taking the BEST case (smallest difference) for write speed on the MBP (747-692) indicates I've lost 55 MB/sec or approximately 7%.  

I was hoping for a more negligible difference, but the real test that matters will be if I notice any significant degradation.