Rockstor VMware environment slow write speeds

So i have a Rockstor VM on esxi 5.5 host with pci passthrough asus pike 2008 raid card, 8 x 3tb seagate constellation es.2 drives. I have 2 issues one being the web interface for rockstor won’t populate S.M.A.R.T saying “Not supported” even though i can run smartctl commands all day with no issues. But i’ll probably make a separate post on that if no one has an easy fix, my main issue is with my write speeds. It seems to me what is happening is the machine is caching data into ram before writing it because i will get fast write speeds for the first multiple gigs of data ~80-100mb/s over network or 300+mb/s on the machine. After ~20gbs of data it will slow to a crawl ~1-5mb/s write speeds. The machine has 8 cpus 32gbs ram and is installed on a ssd datastore. If anyone needs logs to get more information on my issues just let me know what you need, everything has been running fine just been an ongoing issue i’d like to get fixed. Thanks.

Last time i ran the write test over a month ago it was even slower than that, but if i run it on a fresh reboot before the server is utilized (writing stuff to it) then it runs fast like it should ~300mb/s

I ran Rockstor on a VM for a while with a LSI card set for passthrough and it recognized SMART. Could it be a issue with the card settings? I was having issues with it keeping the pool after I would reboot the machine so I tried all different kinds of settings and not once had an issue with SMART working. Im running 5.5 as well and its running on a Dell T5500. The issue that I had was after rebooting the machine, whether it be bare metal or the VM, it would lose one of the drives in the pool I had setup. I believe the issue with that was the VM that Rockstor was installed on was getting a new UUID after every reboot. After I gave it a static one I was still having isues and just gave up. I am curious how you got around that issue.
To your other question network speeds were not as fast as they are not that its on a dedicated machine, but it also was sharing one NIC with 5 other VMs. I was getting much faster speeds then what you are reporting.

My raid card is just passing the hdds through to rockstor, so i have no issues with uuid changing or anything reboots are fine never had an issue. I can type smartctl commands all day and rockstor vm can see all information on the disks however the web interface sees nothing. I know my speeds have nothing to do with network, it will transfer at 80-100mb/s for the first like 20-30gigs of data then slows to a crawl and stays at a crawl for awhile, not related to network usage as i can monitor and nothing else is using up the network. Also as i posted a screenshot that it slows down on the rockstor machine itself not just transferring over the network.

Was your problem ever solved?
Because I have the same issue, and for the life of me I can’t figure out whats going wrong