Do SSDs Slow Down As They Approach Full Capacity? (Explained)

Solid-State Drives (or SSDs) are storage devices used in computers. These drives are pretty faster than the traditional mechanical hard disks because they make use of flash-based memory. However, as time goes on the storage space gets full. Do SSDs slow down as storage space is getting full?

There are a couple of things that you need to be careful with when using a solid-state drive (SSD). One of them has a lot to do with how you fill the drive. Here’s the thing; a nearly full SSD tends to slow down your computer because it’s slower write operations.

Is it OK for The SSD To Be Full?

Although SSDs are much faster than hard disks, for you to maintain their performance and speed for a long time, there are a couple of things you need to avoid. First, you need to avoid wiping your SSD as you might end up permanently deleting your data, with no chance of restoring them. This is especially true if your operating system supports Trim.

To enhance the speed and performance of your SSD, another thing you need to avoid is trying to fill your drive. Your solid-state drive certainly needs some free space to perform better and speed up write operations. While this may be surprising to you, it’s pretty simple to understand.

Here’s a brief explanation of why free space matters for your SSD;

• First, you need to understand that there are blocks inside the solid-state drives. If you don’t know, this block is the smallest unit of access on a drive.
• When your SSD has a lot of free space, what that means is that its blocks are empty.
• An almost-full solid-state drive only has a lot of partially filled blocks.

Imagine your SSD is almost full and you go to write a file. Here, the drive will need to read the partially filled block into its cache. After that, the drive will modify the partially-filled block with the new data and then have it written back to the hard disk. This process will continue if the file must be written to more than one file.

As you can see from the above illustration, having an almost-full SSD will only result in partially filled blocks. Unfortunately, it takes a lot of time to write files on this type of drive as it requires reading the files into the cache, modifying the blocks with new data, and then rewriting them into the hard disk.

An empty SSD will never go through all these processes, as there are no partially filled blocks in it.

The bottom line is that writing an empty block is pretty fast. As such, it’s never okay for your SSD to be full. If you must write other files, you need to get another drive once your SSD is 75% full, according to Anandtech.

Unlike in the past, SSDs are very affordable to purchase these days. To strike a good balance between the performance consistency and capacity of your SSD, my advice is that you should go for a solid-state drive with a very higher capacity than what you want.

Do SSDs Slow Down as They Approach Full Capacity?

As earlier mentioned, an SSD that’s 75% full will certainly perform better. However, once the storage status approaches 90%, the SSD will start to slow down. Of course, there are a couple of reasons why that’s so.

The closer your SSD is to its full capacity, the more the number of partially filled blocks that it’ll possess. I’m sure you know the exact implication of having partially filled blocks.

I’ve mentioned it before but will say it again, an SSD that’s approaching its full capacity has a lot of partially filled blocks. If you end up writing files to this drive, a couple of things will happen.

The SSD will start by reading the partially filled blocks into its cache. From there, it’ll proceed with modifying its value and then writing it back into the drive. Generally, this process requires a lot of time but you can always avoid it.

One way to avoid poor performance and speed of your solid-state drive’s write operations is to avoid making them reach their full capacity. I repeat, 75% is okay; the SSD doesn’t have to be filled up.

The bottom line is that SSDs will most certainly slow down their write operations when they approach their full capacity. So, you need to avoid it at all costs.

At What Capacity Do SSDs Slow Down?

You need to keep in mind that SSDs don’t slow down when reading files. The slowing down process comes in when the drive is in use to write various files. Furthermore, the slowdown issue is often caused by the lack of contiguous blocks during the writing phase.

Earlier in this post, I mentioned that an empty SSD certainly has empty blocks. However, a solid-state drive that’s almost approaching its full capacity has a lot of partially filled blocks.

With empty blocks, things become pretty fast and easy during the write-up stage for the files. However, I can’t say the same for partially filled blocks, as they often require a longer process during the writeup stage.

Having a lot of free/empty blocks means your drive will just write the file directly. It won’t replace any data. If you don’t know, SSDs often come with firmware. The firmware will assist in collecting any garbage. Unfortunately, for your SSD’s firmware to work perfectly, it needs space. This explains why you need some space on your solid-state drive to speed up the write operations and achieve high performance.

Speaking of capacity for the slow down to occur; We’ll say that anything above 75% could make the SSD misbehave. So, stick to 75% and once you notice that your SSD is on the mark, you need to stop writing more files into it. Some experts often advise sticking to 80 percent or 85 percent. If it works for you, you might need to stick to it.

Why is My SSD Slowing Down?

Several factors could contribute to why your SSD is misbehaving and slowing down during its write operations. First, slow down may occur if your SSD is full or approaching its full capacity.

Apart from that, you need to understand that an SSD will certainly slow down if your computer’s SATA controller doesn’t run in the Advanced Host Controller Interface (AHCI) mode. One way to check is to enter BIOS and go to the configuration area. If AHCI is off; all you need to do is to enable it.

Also, if the TRIM technology is not working, it could make your SSD slow down. This technology is specifically designed to allow your operating system to inform the SSD that certain data blocks are not necessary and need to be deleted.

So, if the TRIM is not enabled, there’ll be a lot of unnecessary data blocks on your drive. This, of course, is not a good one for your SSD’s performance.

Disk defragmentation is another common reason why SSDs slow down. To improve the performance of your SSD, you need to avoid it at all costs.