8D using SSD as main drive

Currently 3x 10TB 7200rpm, 4 x 6TB 54000rpm, 1 x 3TB 5400 rpm and Plexor 256GB accelerator.
The 3TB is flashing red and now needs replacement.
As SSD prices have become reasonable, and boosting speeds would be a worthwhile target, thus I was wondering how much speed improvement will I get if I put in a 4TB Samsung 870 QVO, and whether that is recommended at all.
Further down the line one of the 6TB is also reporting warning and if going for 2x 4TB SSD will be a better route.
Has anyone had any experience either with the 5D3, 5D or 8D?

----- Update 1 -----

Since I wrote the above, I have read up on the 8D and it mentions Data-Aware Tiering in the Data Sheet. I had to read up to the B1200i ’ info http://www.drobo.com/downloads/products/QA-0118-00_drobo-ssd-tiering-faq.pdf to understand the quite significant performance boost.
No I don’t know how it would work in conjunction with the dedicated SSD slot in the back, but this seems to mean 2 main slots with SSD’s will be designated 'transactional tier" of storage (using Drobo’s parlance), and this will not be added to the main storage capacity.
Thus current 42.33TB Data capacity will drop to 33.41TB when the “Hybrid Storage Option” which changes 2 drives into SSD’s on the Capacity Calculator page and the problematic 3TB and 6TB drives are taken out.
At least this information on the SSD means I do not have to spend that much on 2x 4TB SSD’s which are expensive, but can go for cheaper and smaller SSD’s.
The Capacity calculator mentions 240GB, and there is no mention on optimum size for larger capacity. I’m guessing perhaps using the B1200i literature as a guide (it mentions 18TB), so multiplying the 240GB going at that time by 4x might bring us to >72GB capacity and 1GB SSD to take that load.

Any insights, experiences or comments will be appreciated !

After adding SSDs to the Drobo B1200i, performance will increase:

  • Over 2x transactional workload performance (IOPS)
  • Up to 30% increase in streaming performance (MB/s)
  • Almost 3x application scalability (Microsoft Exchange mailboxes)
    For a small increase in price, this technology delivers a significant increase in performance.
    No, SSD support and Automated Data-Aware Tiering is available only on the B1200i at this time.

----- Update 2 -----

I purchased 2x 870 1TB QVO and replaced the failed 3TB.
The screen above indicates that the new SSD is specifically recognized. I have never seen that icon before!
Also do notice the Warning below which states " Transactional Tier is disabled. For single disk redundancy Drobo requires 2 SSDs in addition to 2 other hard drives."
So this means there is hope that this “Hybrid Storage Option” in the drive configurator is Actually the “Data Aware Tier” feature of the 8D and B1200i.

I feel Drobo should put this in their manual and promotional materials and indicate how much faster it actually performs. They should do tests for 5400rpm drives + 2x SSD, as well as 7200rmp drives + SSD, 7200rpm drives only, and 5400rpm drives only. Performance matters a great deal to users. The older Gen1 and Gen2 were alway a bit leisurly, as were the NAS models.

Meanwhile, after I backup my Volumes, I will insert / remove additional drives to try to activate the 2 SSDs into “Transactional Tier” mode.

----- Update 3 -----

This shows after rebuild of replacing the 6TB with the 10TB.
Notice the Hot Data Cache SSD is “On”, as well as the Blue SSD slot indicator has a green status light.
I have 1 single SSD inserted but “Transactional Tier” is not “On” (it needs 2 SSD’s)

This next Snap shows I have further removed a 6TB drive and inserted another 1TB SSD.
This 2nd SSD has now activated “Transactional Tier” as well as the Hot Data Cache from the backside SSD slot from previous. This 8D now has 3 SSD and 6 HD’s (2x 5600rpm, 4x 7200rpm).

As it is rebuilding and I still have two 5600rpm Red Drives, I will not know the transfer speeds until later, but I hope it can surpass the earlier numbers.