In my professonal role I use quite a lot of disks and the performance of the disks I use have a direct impact on costs to the buisnesss. As a result I have spent consideralble time researching how to squeeze that last drop of performance out of disks even if they are already fast out of the box. Paying attention to these small details is how one can optimize fixed storage performace.

Leaving unallocated space on an SSD can help optimize wear leveling and garbage collection, contributing to better performance and longer lifespan. Here’s how much space you should consider leaving unallocated:

General Recommendation

• 10-20% Unallocated Space: It’s generally recommended to leave about 10-20% of the total SSD capacity unallocated. This space gives the SSD controller more flexibility for wear leveling, garbage collection, and managing bad blocks.

Why This Matters

• Wear Leveling: SSDs use wear leveling algorithms to distribute write and erase cycles evenly across all memory cells. Unallocated space provides additional room for these operations, preventing any particular cells from wearing out prematurely.
• Garbage Collection: SSDs periodically reorganize and clean up partially used blocks, a process known as garbage collection. Having extra space available allows the SSD to perform this task more efficiently, reducing write amplification and improving performance.

How to Implement This

• Manual Partitioning: When you set up partitions on your SSD, simply create partitions that use 80-90% of the total capacity, leaving the rest unallocated.
• Over-Provisioning Feature: Some SSDs come with built-in over-provisioning, where a portion of the drive is already reserved for these purposes. If your SSD supports this feature, you might not need to leave as much unallocated space manually, but adding more can still be beneficial.

When to Adjust

• Heavy Write Workloads: If your SSD will be subjected to heavy write operations (e.g., video editing, database management), leaning towards the higher end of the 10-20% range or even more can be beneficial. All of the work that I do results in heavy write workloads, so I have started to leave 20% slack in new disks by default.
• Consumer vs. Enterprise Drives: Consumer-grade SSDs typically benefit from 10-20% unallocated space. For enterprise drives, which are designed for much heavier use, the manufacturer’s guidelines may suggest different amounts, or the drive might already be optimized with built-in over-provisioning.

Conclusion

Leaving 10-20% of your SSD unallocated is a solid guideline for optimizing wear leveling and garbage collection. This practice can help maintain consistent performance and extend the life of your SSD.