Re: SSD Analyzer Tool

On 12/3/2011 9:35 PM, John Jones wrote:

He had a drive fail. We have no idea if it was a memory cell that failed,
a full memory chip, the controller chip, the SAS interface chip, the buffer
memory chip, or some other piece. Also, there are typically 4-10 memory
chips on an SSD; if 1 chip failed v. just a cell then it would probably
take out enough space that the drive couldn't compensate.

Is it your belief that a drive that had a cell fail rather than a chip would report it to the system? If not, then the distinction is moot - eventually enough cells will silently die that the drive will no longer be able to compensate. I agree that losing a chip is a catastrophic event. My point was only that the drive ought to let the system about degrading cells; it's pertinent information for systems administration.

As to having the extra cells, they are actually used for performance with
added reliability being a side benefit. Writing a normal cell is a read
cell/update buffer/erase cell/write cell operation, but cells in the spare
area are already erased so only a write is needed to store the data (the
cell being updated is mapped to the new cell& the old cell is put on the
list of cells to garbage collect). So the extra cells aren't a reserved
area so much as cells that wind up scattered all over the memory chips over
time. Depending on the drive's firmware& OS, the garbage collection of
used cells - where they're erased& prepped for future writing - occurs
when the drive is idle or the OS issues a TRIM command.

This is a very cool concept. Clearly SSD technology has progressed significantly. Personally, I'm leaning towards a combination of SSD and HDD on my next workstation. I'm just not sure yet that it's ready for the enterprise, especially at the current price point, but we'll see.

Joe