SOLVED - New UNRAID 6 build. Question about PCIe SAS HBA extender for additional SATA ports.

[albatr0ss]

Hi all,

I am going to set up a new UNRAID server in the near future to migrate al my dockers and plex server from my NUC device handling all the stuff.

 

Expected use of UNRAID server:

- Plex server (local 4K direct stream, 1-2 1080p remote direct stream)

- *arr dockers

- plexmetamanager

- Overseer

- Tautulli

- Photprism

- NextCloud

- pihole

- vaultwarden

 

Hardare:

- Motherboard MSI PRO B760M-A WIFI DDR4

- CPU Intel Core i3-12100F

- RAM Corsair 2x8GB

- GPU Nvidia P400 (mainly for h265 transcodes)

- Power supply Corsair 850W

- 3x4TB WD RED HDD

- SAMSUNG MZ-7TD250BW, SSD 250 GB (for cache, to be changed with 2TB WD RED NVMe)

- Fractal Design Node 804

 

The motherboard has 4 SATA ports so I will be using those to start off. I think that for a start a 8TB storage (2x data drives + 1 parity drive) will be fine. But I want to future prove my build as I have plenty of HDD slots free in the Fractal Design Case. Therefore I was planning in installing a SAS HBA controller to add additional SATA ports to the main board as need arises like the LSI 6Gbps SAS HBA LSI 9211-8i.

 

The motherboard has two PCIex16 slots:

- 1 PCIe 4.0 x16 slot (offering x16 lanes) I will use for the Quadro P400 GPU

- 1 PCIe 4.0  x16 slot (offering x4 lanes) I would like to use for the SAS HBA controller

 

Question:

Will the PCIe 4.0 x4 slot be able to handle all the four SATA drives I would like to connect to it?

 

I made to following reasoning using information found at the following post 

 

SAS HBA controller has PCIe 2.0 x8 connection

Motherboard has PCIe 4.0 x4 connection

installing the controller into the slot (possible because it is a x16 but with x4 lane) will fallback negotiating a  

 

PCIe 2.0 x4 connection

 

this, if my math is correct, should guarantee a max transfer rate of 2000MB/sec which should give 250MB/sec each drive. 

Given that WD RED drives max out at 180MB/sec this should be more than enough to connect additional 8 drives to the SAS HBA controller connected to a downgraded PCIe 2.0 x4 port on the motherboard.

 

Anybody with more experience can confirm this? Thank you!

[JorgeB]

8 hours ago, albatr0ss said:

this, if my math is correct, should guarantee a max transfer rate of 2000MB/sec which should give 250MB/sec each drive. 

There's always some overhead, you should get around 1600/MB/s usable.

[albatr0ss]

Thank you Jorge,

this would still suffice as it would be 200MB/sec if all 8 disks would be accessed concurrently (which I think will never happen given to how UNRAID works).

My main concern is the PCIe x8 card working in the PCIe x4 slot, will this work?

[JorgeB]

21 minutes ago, albatr0ss said:

which I think will never happen given to how UNRAID works

During parity check/sync, disk rebuilds and all writes if turbo write is enabled.

 

22 minutes ago, albatr0ss said:

My main concern is the PCIe x8 card working in the PCIe x4 slot, will this work?

It should work fine, unless there's some incompatibility with that board.

[albatr0ss]

Thank you Jorge!