My SSD used to be so much faster but has recently slowed down... What happened?

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Crucial SSDs have a maintenance feature called Active Garbage Collection built into the controller. Active Garbage Collection is triggered when the SSD has power but no data throughput, and does background cleanup on the SSDs. The purpose of this feature is to maintain the SSD's performance in environments where for any reason TRIM (discussed here) is not a possibility, by cleaning out the cells on the SSD as data is removed. If TRIM is present it will handle this background cleanup, but if for any reason TRIM can't reach the SSD, Active Garbage Collection is there to take care of the drive.

However, in order for Active Garbage Collection to have an effect, the SSD needs to have periods of idle time, since that is the only time when the feature is able to run. If the SSD is not given any idle time, for example in a computer that is powered on, constantly working, and then immediately powered off, then Active Garbage Collection will never be triggered. Almost as important as idle time, is that the SSD has empty space to work with. TRIM and Active Garbage Collection both rely on the ability to move data between sectors as a part of the clean-up effort, and without sufficient empty space on the SSD, the clean-up will either be ineffective, or worse, won't take place at all.

An SSD that is not receiving TRIM commands and where Active Garbage Collection never runs properly, will never have the cells on the drive cleaned out after data is deleted. That will over time lead to an accumulation of 'junk' data, which slowly will clog up the drive. Eventually this well result in a drop in performance, and sometimes freezing during use of the SSD.

If that has happened to your SSD, you may simply need to force Active Garbage Collection to run on the drive by powering the SSD on and leaving it idle for 6 to 8 hours. After that, your drive’s functionality and performance should be restored.


Follow these steps to trigger Active Garbage Collection on your Crucial SSD:

On a desktop PC, simply disconnect the SATA cable from your SSD and only leave the power cable connected. After switching your PC on, the SSD will be in an idle state but still have power so Garbage Collection can function. On a laptop, power on with the SSD installed and enter your system BIOS (please refer to your system manufacturer’s documentation on how to access the BIOS.) Leave the laptop in the BIOS menu for the 6-8 hours.

On a Mac, press the Options key while powering on to enter the Startup Manager screen. Leaving the Mac on that screen provides the SSD with power but keeps it in an idle state so Garbage Collection can function, just like the BIOS screen on a Windows laptop.


To prevent the SSD performance from degrading again in the future you can adjustment your power settings, to make sure that the SSD stays powered on when your computer goes into sleep mode.

In Windows:

- Go to Control Panel
- Go to Hardware and Sound
- Go to Power Options
- Select Change Plan Settings
- Select Change Advanced Settings
- Make sure the 'hard disk' field is set to ‘never’ (Laptop users select 'battery and power adapter').

On a Mac computer:

- Go to System Preferences
- Go to Energy Saver
- Make sure  'Put the hard disk(s) to sleep when possible' is unchecked.



Kilobyte Kid

Yes I accept that the read/ writ speed at SSD is much faster than HDD but the accumulation of clutters can bring issue to its speed. As mentioned above the Garbage Collection method can be helpful in this regard.


Kilobyte Kid

My speed ratings were initially dismal, but I discovered that Lenovo had artifically capped the disk access speeds. After reflashing my BIOS (on an X61 tablet -- here), I am now up to SATA II speeds (about 260 MB/s).


Now I've set my drive never to power off, supposedly even when the computer is asleep. How can I confirm that garbage collection is taking place during sleep? Is there some field in one of the SSD info utilities (e.g. CrystalDiskInfo) that I can monitor to confirm that garbage collection is taking place?


Do I have to run the machine for 6-8 hours booted up into the BIOS, as suggested above, or can I just let it sleep for 6-8 hours to achieve the same result?


Also, I found that Win7's defragment utility was still scheduled to run by default after a clean Win7-64 system install on the SSD. I thought Win7 was suppposed to sense that the drive is a SSD and disable defrag?


I've subsequently disabled the scheduled defrag. Is that the right thing to do, or will Win7 sense the SSD when the scheduled defrag is triggered and do something else that is beneficial to the SSD, like this TRIM stuff discussed above?

Kilobyte Kid
I'm starting to doubt the advice given above: "To prevent the SSD performance from degrading again in the future you can adjust your power settings, to make sure that the SSD stays powered on when your computer goes into sleep mode."
I've changed the power setting to never let the SSD power down. Yet every time the machine sleeps, I see that the "power on count" in CrystalDiskInfo increments by one.
Kilobyte Kid
I just want to share that after 2 years of use and a clean install of macOS, My 960gb M500 drive suddenly got really slow, below HD speeds. With some difficulty. as I couldn't even make a USB-disk of the MU05 update that would boot my PC laptop, to which I moved  the M500, and I had to find a CD and somehow managed to find an old RW, burnt it and boot and applied. Then I removed the CD and left the PC running with the M500 for 8 hours or so, nothing obviously booted or in use as this is a Mac partition. Now tonight I moved it back to my MacBook Pro and write and read speeds are around 400 MB/s. Garbage Collection when really idle  seems to work fine. I'm contemplating activating trim, but I want to check for sure macOS Sierra's trimforce doesn't send queued trims as I understand at least Linux distributions with this could damage the drive. It says so in Wikipedia.