SSDs are fast and can easily handle audio, video and film but compared to hard disks they are expensive.
Material in M & E is organized in projects using folder/subfolder structures. So the ideal M & E solution is a shared storage system with an SSD cache and hard disks with transparent project content caching.

So how to get to transparent caching of project content?
It is the directory tree, which shows what is on the storage. Now a question is: can the DDP copy and move project content around without effecting the directory tree?
Normally when a copy or move is done this shows in the directory tree. However these days systems consist of groups of hard disks, SSDs or tapes on premises or in the cloud.

To manage this a file system with its directory tree is kept independent from where the content is stored.
This creates the possibility to move content (file data) around internally between these groups without effecting the directory tree. However at the end of a move the directory must become aware of the new position.
At that moment user file access is not possible. A copy would not be possible for also another reason because it means there would be two positions and one directory entry.

Now with A/V FS we have gone that extra mile and implemented a mechanism to move or copy projects around internally while operator access projects as they see fit without hick up.
Assume A/V FS has defined a SSD group as Cache. Just by opening the project the caching of the content can start.

Furthermore when the project is finished its content can be instantly cleared from the cache.
This is because A/V FS has a unique property built in. The data of files and folders in the directory tree can be at two places simultaneously.
Without this property transparent internal copies or moves of projects and files are not easily possible.
How come? Well, lets analyse the move of a file as example. A move is a copy, rename and then finally delete of the original. Now a file being read by an operator can not be deleted.
This means that although the copy part can happen the rename and the delete must be stalled to the point that no one has access to the file or files anymore.
But when would that be? There is no simple answer here unless investing in a DDP.