What is the current state (2016) of SSDs in RAID?

There are plenty of resources available online that discuss using SSD drives in RAID configurations - however these mostly date back a few years, and the SSD ecosystem is very fast-moving - right as we're expecting Intel's "Optane" product release later this year which will change everything... again.

I'll preface my question by affirming there is a qualitative difference between consumer-grade SSDs (e.g. Intel 535) and datacenter-grade SSDs (e.g. Intel DC S3700).

My primary concern relates to TRIM support in RAID scenarios. To my understanding, despite it being over 6 years since SSDs were introduced in consumer-grade computers and 4 years since NVMe was commercially available - modern-day RAID controllers still do not support issuing TRIM commands to attached SSDs - with the exception of Intel's RAID controllers in RAID-0 mode.

I'm surprised that TRIM support is not present in RAID-1 mode, given the way drives mirror each other, it seems straightforward. But I digress.

I note that if you want fault-tolerance with disks (both HDD and SSD), you would use them in a RAID configuration - but as the SSDs would be without TRIM it means they would suffer Write-Amplification which results in extra wear, which in turn would cause SSDs to fail prematurely - this is an unfortunate irony: a system designed to protect against drive failure might end-up directly resulting in it.

So:

1. Is TRIM support necessary for modern (2015-2016 era) SSDs?

   
   
   

   1.1. Is there any difference in the need for TRIM support between SATA, SATA-Express, and NVMe-based SSDs?




2. Often drives are advertised as having improved built-in garbage-collection; does that obviate the need for TRIM? How does their GC process work in RAID environments?

   
   
   

   1.1. For example, see this QA from 2010 which describes pretty-bad performance degradation due to not-TRIMming ( https://superuser.com/questions/188985/how-badly-do-ssds-degrade-without-trim ) - and this article from 2015 makes the case that using TRIM is strongly recommended ( http://arstechnica.com/gadgets/2015/04/ask-ars-my-ssd-does-garbage-collection-so-i-dont-need-trim-right/ ). What is your response to these strong arguments for the necessity of TRIM?




3. A lot of articles and discussion from earlier years concerns SLC vs MLC flash and that SLC is preferable, due to its much longer lifespan - however it seems all SSDs today (regardless of where they sit on the Consumer-to-Enterprise spectrum) are MLC thesedays - is this distinction of relevance anymore?

   
   
   
   

   1.1 And what about TLC flash?




4. Enterprise SSDs tend to have have much higher endurance / write-limits (often measured in how many times you can completely overwrite the drive in a day, throughout a drive's expected 5 year lifespan) - if their write-cycle limit is very high (e.g. 100 complete writes per day) does this mean that they don't need TRIM at all because those limits are so high, or - the opposite - are those limits only attainable by using TRIM?