SSD and Defragmentation

[vmachiel]

Hi,

So i read somewhere that Mac OS X automatically defragments your hard drive. I also read that SSD's don't need to be defragmented and that it can actually reduce it's life span. Now that i've manually installed a SSD, will OS X still defragment it? And if so, can you disable this?

Thank you!

 

[ScoobyMcDoo]

Hi,

So i read somewhere that Mac OS X automatically defragments your hard drive. I also read that SSD's don't need to be defragmented and that it can actually reduce it's life span. Now that i've manually installed a SSD, will OS X still defragment it? And if so, can you disable this?

Thank you!

As best I can tell there is no "background automatic defragmentation" that OSX does as some folks have suggested. Instead they use techniques in writing data to avoid fragmentation in the first place. If you read Apple's articles on the subject, you will find they never mention defragmentation - they use the term optimization.

 

[vmachiel]

aah ok, well that's one less problem then

 

[ICEBreaker]

According to Amit Singh's article Fragmentation in HFS Plus Volumes, which mind you was written in 2004 in the days of Panther, Mac OS employs a two-pronged approach of On-The-Fly Defragmentation and Hot File Clustering to reduce the level of fragmentation. I don't know about the OTF defragmentation, but Mac OS X does utilise hot file adaptive clustering. Read more About disk optimization with Mac OS X.

 

[Quad5Ny]

In addition to the hot band, OS X will try to defragment a file when opening it if all these conditions are met:

• The file is less than 20MB in size
• There are more than 7 fragments
• System has been up for more than 3 minutes
• A regular file
• File system is journaled
• The file system is not read-only

Source: http://www.diskeeper.com/blog/post/2011/02/02/Mac-defrag.aspx

OS X does not do full disk defragmentation like Windows. I doubt this would have any large effect on SSD life.

I would be more concerned about page-outs (if your low on RAM) and the sleep (hibernation) file. And even then, your SSD will probably outlast your computer.