DirectStorage initially had a requirement of volume size, that value was 1TB, which now seems to have been changed. 

According to the official specs you would need an NVMe SSD of at least 1TB to use the feature, however, Microsoft has changed the requirements and now requires merely an NVMe SSD. According to Microsoft, DirectStorage allows "games to load quickly thanks to the graphics card without the need for this task to be only the CPU. " Also at the event, it was said that "this enables us to experience incredibly detailed game worlds rendered at the speed of light without long load times." Initially, some people bummed out by the requirement of a minimum 1TB of storage on NVMe SSDs, however, it appears that Microsoft has removed this requirement from the official specifications for Windows 11.

“DirectStorage requires an NVME SSD to store and play games that use the 'Standard NVM Express Controller' and DirectX12 GPU with support for Shader Model 6.0.

Nvidia had already announced last year a technology called RTX IO, which would allow lossless data compression through the GPU to optimize the use of SSDs. This technology must be implemented in conjunction with DirectStorage to, in addition to providing greater access between system storage and VRAM, to use the GPU to compress these files and further accelerate the entire process. According to NVIDIA RTX IO, it should not have any limitations regarding the storage size of SSDs and DirectStorage. This reinforces the message that the user does not have to worry about the storage size of their SSD to take advantage of DirectStorage in Windows 11.

Microsoft removes mandatory >1TB storage requirement for DirectStorage NVMe SSDs