Poor Raid 10 performance even with SSD cache disk

[Naspir]

Hi everyone,

so I have a small NAS with Windows Server 2016 on it, that has the following specs:

- Intel Core i3-3220
- 8 GB RAM
- 4 x 3 TB IronWolf HDDs configured as RAID 10 via the BIOS Raid controller
- 1 x 256 GB SSD as System disk

- 1 x 256 GB SSD configured as RAID Cache (64 GB) the rest is formatted as an extra partition

- HP NC523SFP 10Gb network adapter

 

I have a editing / gaming workstation directly connected via the 10G interface. After I'm done editing I offload the video/photo material to the NAS or I even edit directly from the NAS.

 

This is my problem:

When I transfer files large files, the first 1-2 GB go really quickly (around 700 MB/s) but then it rapidly slows down and goes to a crawl speed of around 10 MB/s. It then continues to have short boosts of up to 280 MB/s before slowing down again to 10MB/s every time and staying there for about 20 seconds. (see attached picture!)

 

To me it looks like some kind of buffer is filling up and when it does, everything comes to a stop. I just don't know how to fix it as 10 MB/s is not even close to the usual write speed of an HDD and even further away from a RAID 10. I thought that adding a Caching SSD via Intel RST would help, but it actually did nothing.

 

I also already verified, that it has to be the RAID and not the network card. When writing to the formatted partition of the Raid Cache disk via the network, it goes right up to max. SATA speed of 6 Gbps without any issues.

 

Does anyone have any ideas?

 

EDIT: When running HD Tune, the speeds actually look fine as well. It's only when actually transfering files in the real world that things are slow.(See attached HD Tune Test results for the RAID)

EDIT2: I attached also an 8GiB CrystalDiskMark Test... Random writes look very low.

 

 

Edited October 6, 2021 by Naspir

[Naspir]

Really no ideas from anyone?

[wseaton]

Onboard Intel RAID and SSDs don't mix. I had nothing but problems with this combo on 2016 and I'm surprised you got this to work at all. Server 2019 pulled the plug on RST entirely. Intel is now just focusing on Optane, and enterprise only.

 

One way to prove this is to try running one of the SSDs off a non RAID SATA port by itself and see if benchmark improves.