I’ve wanted to install a solid-state drive (SSD) in my laptop for some time because of the dramatic boost in performance and responsiveness. However, I’ve been reluctant to buy one because I use full disk encryption (FDE) on my laptop, and I wasn’t sure how it would affect the speed of the SSD.
Unfortunately, there is not a lot of concrete information on the Web for the impact of FDE on SSD’s other than this gloomy blog post from November 2009. The author of this post used Utimaco Safeguard Enterprise to encrypt a Intel X25-M G2 160Gb SSD in a Dell Latitude E6400. Disappointingly, he found that with FDE, the SSD performed as slow or slower than the same laptop with an encrypted conventional hard drive. Clearly, in this scenario, there is little benefit to justify the cost of an SSD.
However, I use PGP 10 Whole Disk Encryption (WDE), one of the leading disk encryption products, which has just been updated with better support for SSD’s. I finally decided to purchase an SSD, and since I can’t find any other benchmarks for encrypted SSD online, I decided to perform my own.
The Setup
I have a Macbook Pro 17″ (Core 2 Duo; late 2009). It used to have a Seagate Momentus 7200 RPM drive, one of the faster conventional laptop hard drives on the market, and, as stated above, it was encrypted with PGP 10 WDE. As a baseline, I used Xbench to test how fast the drive performed.
Here are its scores:
Xbench Disk Test score: 36.64
Sequential 53.83
Uncached Write 73.59 45.18 MB/sec [4K blocks]
Uncached Write 52.87 29.91 MB/sec [256K blocks]
Uncached Read 37.01 10.83 MB/sec [4K blocks]
Uncached Read 67.64 33.99 MB/sec [256K blocks]
Random 27.77
Uncached Write 9.65 1.02 MB/sec [4K blocks]
Uncached Write 81.84 26.20 MB/sec [256K blocks]
Uncached Read 69.42 0.49 MB/sec [4K blocks]
Uncached Read 72.43 13.44 MB/sec [256K blocks]
I also performed some practical, “real-use” tests as follows:
Opening iTunes: 17 seconds
Opening Papers (PDF manager): 45 seconds
Opening VMWare Fusion and resuming a Windows XP VM with 512MB RAM: 50 seconds
Opening Microsoft Word: 24 seconds
Opening PASW 17 (SPSS): 24 seconds
Copying a 5.73 GB bzip file from one part of the hard drive to another: 4 minutes, 25 seconds.
Boot time from when the PGP passphrase is typed in to the OS X login screen: 1 minute, 16 seconds.
Login time from inputing password to when the Dock appears: 20 seconds
Time for start-up applications (Things, Skype (www.skype.com), and Snapz Pro X to load after inputing login password: 1 minute, 18 seconds.
All told, it took 2 minutes, 34 seconds to boot and load my start-up applications so I could begin using my computer normally.
The Unencrypted SSD
For comparison, I replaced the Seagate Momentus with a Crucial RealSSD, which as of April 2010, is one of the fastest SSD’s available.
Here are the same tests performed with the Crucial RealSSD unencrypted:
Xbench Disk Test score: 300.13
Sequential 184.15
Uncached Write 254.02 155.97 MB/sec [4K blocks]
Uncached Write 216.33 122.40 MB/sec [256K blocks]
Uncached Read 95.35 27.91 MB/sec [4K blocks]
Uncached Read 373.91 187.93 MB/sec [256K blocks]
Random 810.71
Uncached Write 1278.14 135.31 MB/sec [4K blocks]
Uncached Write 406.00 129.98 MB/sec [256K blocks]
Uncached Read 1578.45 11.19 MB/sec [4K blocks]
Uncached Read 947.85 175.88 MB/sec [256K blocks]
Dramatically faster. Here are some real-use comparisons:
Opening iTunes: 3 seconds
Opening Papers: 7 seconds
Opening VMWare Fusion: Loading Windows XP from suspend, 512MB RAM—7 seconds
Opening Word: 6 seconds
Opening PASW: 8 seconds
Copying the same 5.73 GB bz2 file: 52 seconds (five times faster than the encrypted hard drive).
Booting was as follows:
Boot time from Apple logo to the OS X login screen: 24 seconds.
Login time from inputing password to when the Dock appears: instantaneous
Time for start-up applications (Things, Skype, and Snapz Pro X) to load after inputing login password: 4 seconds.
The Encrypted SSD
Now with the tests of the encrypted hard drive and unencrypted SSD as baselines, I fully encrypted the 256 GB SSD using PGP 10 WDE. The process took two hours (which was in itself remarkably fast). Once the encryption process completed, I rebooted and ran the same tests again.
Xbench Disk Test score: 103.12
Sequential 65.10
Uncached Write 78.22 48.03 MB/sec [4K blocks]
Uncached Write 65.20 36.89 MB/sec [256K blocks]
Uncached Read 47.00 13.75 MB/sec [4K blocks]
Uncached Read 83.05 41.74 MB/sec [256K blocks]
Random 247.91
Uncached Write 370.32 39.20 MB/sec [4K blocks]
Uncached Write 120.49 38.57 MB/sec [256K blocks]
Uncached Read 1562.82 11.07 MB/sec [4K blocks]
Uncached Read 222.46 41.28 MB/sec [256K blocks]
As expected, the SSD is substantially slower using PGP WDE. However, it is still much faster than the encrypted 7200 RPM drive. Importantly, the uncached read times are still much faster (between 3 to 22 times faster). Probably for this reason, the user interface still feels very responsive and applications still open very quickly, with little perceptive difference from the unencrypted SSD:
Opening iTunes: 3 seconds
Opening Papers: 10 seconds
Opening VMWare Fusion—Loading Windows XP from suspend, 512MB RAM: 10 seconds
Opening Word—7 seconds
Opening PASW—9 seconds
Boot time was slower than the unencrypted SSD:
Boot time from when the PGP passphrase is typed in to the OS X login screen: 46 seconds.
Login time from inputing password to when the Dock appears: instantaneous
Time for start-up applications (Things, Skype, and Snapz Pro X) to load after inputing login password: 6 seconds.
However, when writing a large file to the disk it was painfully evident that the SSD was much slower in its encrypted state. As before, I copied the same 5.72 GB file:
Copying the same 5.73 GB bz2 file—3 minutes, 49 seconds seconds (three minutes slower than the unencrypted SSD, only a minute faster than the 7200 RPM hard drive).
Summary
Using PGP WDE 10, the SSD is still substantially faster than an encrypted 7200 RPM drive, especially for disk reads. For many tasks, the laptop still feels very fast and responsive (except when large files are written to disk). Therefore, there is value in going from an encrypted 7200 RPM drive to an encrypted SSD—the encrypted SSD is markedly faster.
However, it’s clear that the encrypted SSD is much slower than in its unencrypted form (by as much as two thirds, going by the overall Xbench score). By analogy, encumbering the SSD with FDE is like harnessing a champion racehorse to a plow. However, if you are interested in FDE, security is probably more important to you than raw speed anyway.
Update May 18, 2010:
The above tests show performance before and after encryption for the SSD, but not for the 7200 RPM drive. Robert Silvers, of Photomosaic.com, kindly provided these test results of his Seagate Momentous 7200 RPM drive before and after encrypting with PGP:
Without FDE:
Results 41.56
System Info
Xbench Version 1.3
System Version 10.6.3 (10D2094)
Physical RAM 4096 MB
Model MacBookPro6,1
Drive Type ST9500420ASG
Disk Test 41.56
Sequential 109.91
Uncached Write 121.18 74.40 MB/sec [4K blocks]
Uncached Write 130.87 74.05 MB/sec [256K blocks]
Uncached Read 73.57 21.53 MB/sec [4K blocks]
Uncached Read 144.78 72.77 MB/sec [256K blocks]
Random 25.62
Uncached Write 7.78 0.82 MB/sec [4K blocks]
Uncached Write 139.43 44.64 MB/sec [256K blocks]
Uncached Read 79.93 0.57 MB/sec [4K blocks]
Uncached Read 126.19 23.41 MB/sec [256K blocks]
With PGP FDE:
Results 43.85
Disk Test 43.85
Sequential 58.90
Uncached Write 69.96 42.96 MB/sec [4K blocks] (42% decrease)
Uncached Write 56.13 31.76 MB/sec [256K blocks] (57% decrease)
Uncached Read 47.55 13.92 MB/sec [4K blocks] (35% decrease)
Uncached Read 67.69 34.02 MB/sec [256K blocks] (56% decrease)
Random 34.93
Uncached Write 12.67 1.34 MB/sec [4K blocks] (63% increase)
Uncached Write 93.32 29.87 MB/sec [256K blocks] (33% decrease)
Uncached Read 80.85 0.57 MB/sec [4K blocks] (0% change)
Uncached Read 80.05 14.85 MB/sec [256K blocks] (37% decrease)
About a 46% average loss in performance for 256K blocks.
And here are the results of the same drive using CheckPoint FDE 3.3 for Mac:
Disk Test 41.89
Sequential 53.51
Uncached Write 65.65 40.31 MB/sec [4K blocks]
Uncached Write 43.13 24.40 MB/sec [256K blocks]
Uncached Read 38.09 11.15 MB/sec [4K blocks]
Uncached Read 99.15 49.83 MB/sec [256K blocks]
Random 34.42
Uncached Write 11.57 1.22 MB/sec [4K blocks]
Uncached Write 136.74 43.78 MB/sec [256K blocks]
Uncached Read 82.63 0.59 MB/sec [4K blocks]
Uncached Read 96.35 17.88 MB/sec [256K blocks]
The results overall are slightly slower than those for PGP.