[Solved] LSI SAS controller PCIe 2.0 or 3.0

[surferjsmc]

Hi ppl!

 

It is time to get a SAS controller for my server, will be used only to plug the arrary HDDs (6 drives), no SSDs or NVMEs, PCIe 2.0 ones are cheaper than PCIe 3.0 and would like to know if there is a real advantage regarding read/write speeds if I go for 3.0?.

 

 

Edited October 19, 2021 by surferjsmc

[JorgeB]

1 hour ago, surferjsmc said:

would like to know if there is a real advantage regarding read/write speeds if I go for 3.0?.

Depends on the number and type of devices connected, this will give you a good idea of the performance of both:

https://forums.unraid.net/topic/41340-satasas-controllers-tested-real-world-max-throughput-during-parity-check/

[surferjsmc]

Hi @JorgeB yep i read your tests post and by the way congrats that must be a lot of time and work  but i asked because  it wasn't that clear for me if there is a real difference, to my understanding in most of the scenarios you described speeds are almost the same and looks like besides future proof and SSD usage PCIe 2.0 cards are a good choice.

 

 

[JorgeB]

26 minutes ago, surferjsmc said:

looks like besides future proof and SSD usage PCIe 2.0 cards are a good choice.

Yes, that's why I said to look at the tests, depending on the devices used (and the number of them) it might be the same, and with 6 HDDs it will.

[surferjsmc]

PCIe 2.0 it is

 

Thanks @JorgeB

[JesterEE]

@JorgeB certainly did a lot of the heavy lifting on this one.  I have referenced that post multiple times when making my own HBA considerations a few years ago, and it's probably one of the best data driven studies on the subject.

 

While making your decision, just remember what you're controlling; likely spinning rust (HDDs).  Most of these drives you're likely going to use for your data are moderate speeds (5400 RPM) and have an I/O limit of ~100 MB/s in real world application.  So, while it may be great that your fancy PCIe 3.0 card doubles performance against the PCIe 2.0 counterpart ... do you really need it given the significantly higher price tag?  SDD array, likely yes ... HDD array, probably not.

 

Also be cognizant of the PCI Express lanes your CPU and motherboard combination offer for the application.  Read the fine print on the motherboard specification to make sure you'll be able to use all the lanes that your card offers.  It's not uncommon for the lower priority 16x slots to only be able to source 8x/4x speeds given a consumer grade configuration.

Edited October 19, 2021 by JesterEE

[surferjsmc]

@JesterEE SSD  arrays are far from the average Joe and myself at least for a few years and old rusty spinners are going to last probably a decade more, 2.0 is more than enough for our HDDs.

 

I'll take a look to my mobo's manual and check the PCIe lanes although the majority of them are free besides the ones in use by the graphics card and onboard storage.

 

Thx!