Why can't SSD compression be implemented differently?

[darkfalz]

Well, not at file level, but so the OS "knows" the data is compressed and adjusts free space to boot.

We all know SSDs compress data to increase write speed / wear leveling efficiency. But a 512 GB will only hold 512 GB compressed or uncompressed. Wouldn't it be better if the drive could "tell" the file system about the compression, enabling the drive free space to be reported to the OS as the actual free space, turning a 512 GB drive into a "512 GB minimum" drive instead?

Free space could simply be the uncompressed version amount of actual free space.

I know that the OS & file system drive / partition etc. don't talk to each other on this level, but I'm just saying considering the cost per GB of an SSD it would be pretty nice if you could use that compression to enhance storage size, instead of just wear leveling. Anyone know if this might be in the pipeline for future Windows versions?

 

[Hellhammer]

Only SandForce based SSDs do compression. I've talked to them about it and some enterprise platforms already support varying capacity drives, but the issue here is Microsoft and their unwillingness to implement it. Especially for consumers it might be rather confusing and it would only be supported by a portion of drives.

 

[Quad5Ny]

Did SandForce ever reveal if the compression took place on the Page level or Block level?

I also wonder if each Page/Block is smaller than what it would normally be to store the dictionary, or if the dictionary has its own reserved space thats shared with all the data on the SSD

 

[JellyRoll]

SandForce enables it through DVT, but no support in normal usage is the issue.

DuraWrite™ Virtual Capacity (DVC): a unique SandForce flash controller feature that extends the available storage capacity for typical data beyond the physical capacity of the underlying flash memory. By increasing storage capacity for the same physical flash memory, DVC helps to reduce the cost per gigabyte of delivered capacity to the user. With typical database applications, LSI internal testing has shown that DVC can be used to more than triple the capacity for storing user data. The DVC feature will be demonstrated showing various applications of the technology.

 

[Emulex]

Yeah the problem is finding an OS to support this and what happens when the thin provision space runs out? (hint: bad stuff in windows)