Unraid Expansion, Help needed

[dhendodong]

Hi i plan to expand my current drive count and i would like to ask help in which setup is the best as i do not really how Expander works.

Currently my motherboard has:

X8 GPU
x8 LSI-9201
x4 Free

Here is my Plan(s)

Plan A.

X8 LSI-9201
x8 LSI-9201
x4 GPU(For Display/Transcoding Only)

Plan B.

X8 GPU
X8 LSI-9201
X4 LSI 9211-4i -[FULLY LINKED TO]->(PCIE Riser For Power) Adaptec AEC-82885T 36-Port SAS-3 12Gbps Expander firmware B059 (Sold by Art of Server)

Plan C.

X8 GPU
x8 LSI-9201
x4 LSI 9211-4i

What is my best option and what speed/bw would i get? i think 250MB/ Drive is enough for mine, feel free to suggest a better expander/route where i can get more had drive expansion

Thanks in advance

[Brandon_K]

The GPU is best to be in the x4 slot, regardless, as it has no real use for bandwidth (assuming you're only using it for transcode and not a gaming VM)

Forget about the -4i card.  You can use a 8 lane card in any PCIe slot, so long as it fits.  x8 card in a x4 slot?  It's fine, it will simply drop back to x4 speeds.  500MB\sec per lane with PCIe 2.0, 4 lanes, so 2GB\sec across that card in a x4 slot, which is still WAY more than enough for the 8 drives that you'll potentially have attached to it.  If you were using a chassis with an expander backplane, this would be a different story.

My suggestion would be to pickup a 9207-8i, which is based off of the 2308 chipset, the last of the SAS2 chipsets.  That gets you PCIe 3.0.  While not a directly useful "upgrade" for you now, it may be in the future if you pickup a chassis with a expander backplane.  That will give you the full 48gbps capacity of the card.  If you break that down by drive averaging 250MB\sec, that can support 24 drives at full tilt.  Of course, you're unlikely to ever have that many drives going at full speed with Unraid.  In my case, I have 1 port of a 9207 going to my 12x3.5 backplane in my 2U chassis, 1 port being looped back through to an external SFF-8088 adapter, which connects to a EMC 15x3.5 shelf.  27 drives total connected to the HBA.

For your current scenario;

x8 - 9207-8i (8 drives)

x8 - 9201-8i (8 drives)
x4 - GPU

The Adaptec expander that you listed works the same way that a expander on a backplane does, it's just external.  Since you're direct connecting drives, neither way is particularly better or right/wrong. I would go the 9207 route strictly for upgrade path reasons.   That would also allow you to get rid of the 9201 entirely in the future, freeing up a PCIe slot since it wouldn't need to be filled by either the 9201 or an expander, as the 9207 can handle the entire load of 24+ disks.

Edited January 16, 2023 by Brandon_K