Intel X25M SSD in a MacBook Pro: Performance Degradation Over Time
Xbench score drops 28%
In December 2009, I convinced my employer, xtendx AG, that I needed one of those groovy new Intel X25M G2 Solid State Drives for my then 18 month old early-2008 MacBook Pro. See "Intel X25M SSD in a MacBook Pro: Before and After Performance Results" for details.
A recent blog post from Jeff Atwood's Coding Horror Blog, "Revisiting Solid State Hard Drives" reminded me about one of the reported caveats of running an SSD: Operating systems that do not support the relatively newish TRIM command suffer from degraded performance over time.
Was my system suffering from this too? Time to break out Xbench again and compare the bechmark's numbers.
| Xbench Scores | |||||
| December 2009 | Sept 2010 | Change | |||
| Disk Test | 182.55 | 130.81 | -28% | ||
| Sequential | 115.18 | 85.05 | -26% | ||
| Random | 439.80 | 283.17 | -36% | ||
| Uncached Sequential Speed Metrics (MB/sec) | |||||
| December 2009 | September 2010 | Change | |||
| Write 4K blocks | 84.12 | 44.57 | -47% | ||
| Write 256K blocks | 61.80 | 39.57 | -36% | ||
| Read 4K blocks | 21.04 | 20.60 | -2% | ||
| Read 256K blocks | 115.20 | 105.79 | -8% | ||
| Uncached Random Speed Metrics (MB/sec) | |||||
| SSD | HDD | Change | |||
| Write 4K blocks | 67.60 | 15.06 | -78% | ||
| Write 256K blocks | 64.64 | 67.85 | 5% | ||
| Read 4K blocks | 8.08 | 10.64 | 32% | ||
| Read 256K blocks | 109.16 | 108.25 | -1% | ||
Bummer!The Xbench score drops ~28%! I have absolutely no explanation for the increased 4k random read performance--my gut says it is some sort of odd aberration. In hind sight, I should have saved several runs of the Xbench results from December and averaged them out.
The lost performance due to Flash-drive specific issues can be resolved with the TRIM command, which OSX does not (yet?) support. Windows 7 and Linux 2.6.33 do support TRIM. Many of the existing 'solutions' for my case involve whipping my existing OSX installation from the disk, cleaning this up, and then restoring my Mac to its previous state. Easily a days work, if everything goes well. There is also diglloydTools's DiskTester, which may help. I'll be playing with that next.
Crap.