Re: SSD TBW

On 8/21/2026 3:48 PM, Lawrence D’Oliveiro wrote:
> On Fri, 21 Aug 2026 12:56:40 -0700, Don Y wrote:
> 
>> The firmware in spinning rust controllers has matured over decades.
>> This is not the case with SSDs (especially early entrants to the
>> market).
> 
> First of all, rust isn’t magnetic.

Did you forget the smiley face?

> Secondly, flash-storage firmware is indeed very complex -- most of
> that complexity seems to go into making the device behave like a
> magnetic disk drive. Details are proprietary, but certain filesystem
> experts have voiced the opinion that the firmware implements something
> resembling a log-structured filesystem.

There are also significant differences between consumer, commercial and
enterprise grade devices.  The technology used in the FLASH (SLC, MLC,
TLC, etc.), amount of over-provisioning, size of SRAM buffer, interface
speed/family, etc.  (E.g., I've not yet encountered a SAS or SCA SSD,
not to say that anything -- besides market demand -- precludes their
offerings).  Picking a "sweet spot" that fits a perceived market
demand then becomes the challenge.

> (You know how filesystems nowadays commonly have journals? The journal
> is usually treated as a temporary holding place, to store transactions
> in progress, to allow clean recovery from crashes. But once you have a
> journal, you can consider the regular part of the filesystem to be
> redundant; what if the filesystem itself was all journal? That’s a
> “log-structured filesystem”.)
> 
> You could do away with most of this complexity just by using an
> OS-level filesystem that has wear-levelling built into its allocation
> algorithms. Several of these exist for the Linux kernel, and I think
> are deployed in embedded applications. Unfortunately I don’t think you
> can get regular consumer products designed for such usage, since the
> lowest common denominator, namely Microsoft Windows, has no capability
> to take advantage of them.

It would require a different kind of drive as the role of its controller
would be much different.  Similar to installing FLASH media ("chips")
in a device and taking on the task of managing that memory -- which might
often be "write once" (or write rarely)