Sandforce Life Time Throttling

[gojirasan]

It seems groberts101 is simply denying the existence of life/warranty throttling completely despite the repeated admissions of OCZ and boasts of this "performance throttling" right on Sandforce's web site. OCZ, Sandorce, and Ao1's testing are all obviously wrong. Ao1's data must be some kind of drive malfunction that strangely seems to mimic a data/time curve .

He seems to be asserting the existence of 3 and only 3 states:

1. Fresh. Drive is brand new or has been secure erased. No block assignments in the FTL and all blocks = 1.

2. Garbage collection begins. All blocks have been written too. So Sandforce must reluctantly start recycling used blocks with GC thus theoretically slowing down the drive if they ignored GC initially. This is what he is calling "settled". Why does the controller wait until there is absolutely no choice to start GC? Possibly in order to get higher benchmarks in drive reviews from reviewers who didn't write to every block on their drive before benchmarking. Or it could just be the way the GC algorithms were written. The algorithms may just ignore the "fresh" state because it is so brief.

Ao1 hasn't seen any difference between state 1 and 2. Maybe because most reviewers aren't being sent those small drives for review. So there is no advantage in delaying the normal GC operation. Or maybe at such slow right speeds there isn't any initial speed advantage to temporarily disabling GC.

3. Garbage collection failure. Inadequate GC cannot keep up with sustained writes and the drive has run out of clean blocks to write to. In order to prevent the kind of application interrupting stuttering that Ao1 has been seeing after a TRIM, you throttle the drive down to a speed which the GC process can keep up with. This is a good sort of throttling. Just enough to smooth out the curve. Ao1 hasn't seen this behavior. Probably due to a firmware bug. With sufficiently aggressive GC this short of throttling may not be necessary at all, but such aggressive GC may not be optimal for typical SSD usage patterns in terms of both peak speed and write amplification. So this sort of GC failure is not necessarily a bad thing.

[Ao1]

^ The workload from Anvil's app is not very aggresive. Mostly sequential. If it was 4K random full span, it would no doubt have seen performance degradation.

When I run the app with TRIM deactivated I expect to see performance degradation.

There is also one other form of throttling (and possibly others). Burst throttling.