How badly do SSDs degrade without TRIM?

Solution 1:

I have a OCZ Summit SSD in my work laptop running Win7 x64. I had installed the drive just prior to the firmware update that enabled TRIM so I was running for a long time with no TRIM. I noticed some pretty substantial performance problems after a few months. It became unbearable when, after installing an Apple bluetooth mouse, the cursor would occasionally pause while compiling a large project within Visual Studio 2010. (Also my compile time for this project was then around 20 seconds, up from 13 seconds when the drive was installed initially - though more classes and projects had been added so maybe not the best indicator.)

I backed everything up to my Windows Home Server, updated the firmware (it clears the disk which is why I didn't perform the update prior), restored from backup and performance hasn't been an issue for the past two months since I've done this. (And back down to around 13 seconds for a full compile for the same project.)

So in my experience there is a definite noticeable performance hit over time. This is the reason why I have not yet replaced the HDD in my MacBook Pro with an SSD.

Solution 2:

My understanding of this phenomenon is that it affects the longevity of the drive more than it affects the performance, at least from what an end user observes.

SSD media can only write to empty file pages, but they can only erase a file block (collection of pages, normally around 128). Without TRIM (which the OS uses to tell the drive which pages and blocks it can safely erase), the SSD needs to move pages around in order to free up blocks in order to write new data.

What this boils down to is the SSD needs to perform multiple physical writes to do one logical write of the data sent by the OS. This is a phenomenon called Write Amplification.

The longevity issue comes into play when you consider that SSDs have a limited number of write/erase cycles per cell (1,000-100,000 per cell depending on the media). This is mitigated somewhat by wear leveling which is an automatic use of the least-used cells on a drive to avoid uneven wear, but write amplification limits how much wear leveling can take place. Wear leveling also leads to some write amplification on its own (due to needing to move data which is not changing under certain scenarios).

Since there are still no moving parts in the SSD, it will obviously be much faster than a normal drive even with these issues. However, the relative speed to a non-affected drive could be many times slower depending on how much write amplification is taking place.