Hello guys,
I wanted to setup an HL15 with 15x SATA SSD.
But i saw a video of techno tim : https://www.youtube.com/watch?v=QGSaj5TYUB0 (8:15) saying that the backplane is “limited” to 2GB/s… So basically the SSD speed is up to 500MB/s so with 15x i will saturate the backplane pretty soon…
Am I missing something or it is right ?
Because if it’s right it’s probably better to put HDD with some nvme caching… Same perf for less money…
Thanks for your help
This might be a better video to use as reference. Unless I’m misunderstanding something, I don’t think the backplane will saturate at 2GB/s. Each drive should get SATA or SAS line speed with a dedicated lane directly back to the HBA or controller.
In fact, what better way to use my Friday off than to do a quick test on my HL15 running TrueNAS Scale. 
I have two pools: Z2 8 wide of mechanical hard drives and 2 VDEV Mirror of SSD’s. I was able to push 3GiB/s across those two pools with using fio read test.
capacity operations bandwidth
pool alloc free read write read write
---------------------------------------- ----- ----- ----- ----- ----- -----
Vault15 4.16T 54.1T 1.58K 0 1.24G 0
raidz2-0 4.16T 54.1T 1.58K 0 1.24G 0
3c5b14e8-c94b-4424-99e2-e92d693d3831 - - 192 0 155M 0
502f6f6c-c754-4834-8cb5-f2cc49583b3c - - 219 0 176M 0
33f5799e-9b4b-40c7-bdc8-841c20e1c19c - - 234 0 180M 0
baa07f3d-af76-4a6a-8543-fa7c89350842 - - 175 0 141M 0
4ec7fe6b-6b97-49f7-a641-d27b0a3db26f - - 225 0 172M 0
f4fdf9d5-aa43-4b0e-a978-a89a471d37ef - - 233 0 176M 0
b226c455-084c-4dd7-bb75-2ac5af537fa2 - - 166 0 136M 0
c6a7ad8a-c83b-467b-8463-ad88528bf50f - - 167 0 137M 0
logs - - - - - -
mirror-4 552K 93.0G 0 0 0 0
a8fc9875-d5f8-4942-a6cd-21bde2cd61dc - - 0 0 0 0
95d3c5e6-3173-4243-b156-3c8474386d5a - - 0 0 0 0
---------------------------------------- ----- ----- ----- ----- ----- -----
Vault15-SSD 1.26T 6.44T 12.0K 0 1.50G 0
mirror-0 644G 3.00T 6.19K 0 793M 0
aa3ed5ee-3b05-4eda-91e0-56ee7c249d09 - - 3.04K 0 389M 0
03602ffa-fc83-407f-8d57-de1fd76a041b - - 3.16K 0 404M 0
mirror-1 646G 2.99T 5.82K 0 745M 0
2a409eed-71ae-441c-849e-4f7a88e7d421 - - 2.90K 0 371M 0
62ec60a3-0fbd-428d-886e-22209668009e - - 2.92K 0 374M 0
special - - - - - -
mirror-2 3.01G 461G 0 0 0 0
7754e1bf-de35-49a7-afb2-821dbb93cf1b - - 0 0 0 0
f7489130-78de-42f3-8fcd-d89ae71f4960 - - 0 0 0 0
---------------------------------------- ----- ----- ----- ----- ----- -----```I’d say the 2GB/second number is in reference to over the network peak performance of the standard full build HL15. Here’s the explanation a little lower in the main page that @technotim is showing.
Thank you so much crystal clear !
So my config will definetely provide more speed 
Just wanted to be sure that i will not be limited by the backplane.
Again thanks a lot @rymandle05 for spending time on it !
