HDD / SDD speed question

[chuga]

Hi,

I am getting ready to add a few drives and bought LSI SAS 9211-8i card (and got it working after figuring out the 'tape mod').

 

my build is quite old (but working ok) with a Gigabyte GA-Z68A-DH3-B3 motherboard.   Before adding any thing I started to wonder if I had things plugged into optimal slots.

 

The MB has 2 6GB SATA ports, and 4 3GB SATA ports.   I currently have all 6 ports used (1 ssd cache drive and 5 HDD including parity).

 

In regards to PCIe slots, the board is version 2.  I have a nvidia T400 in the x16 top slot.

 

I put the LSI card into the X16 "x4" slot.

 

Then I realized I was not sure if I was bottlenecking something.  It looks like a PCIe X4 version 2 has a 2GB/s speed which would be slower than any of the onboard SATA slots.  

 

Assume I should have the SSD in the onboard 6GB port?   And if I add a 2nd SSD for dual cache I should use the other 6GB onboard.

 

For HDDs -   will I see a performance difference using onboard 3GB/s port versus the LSI card sharing a 2GB/S PCIe 4x slot?

 

thanks for any comments / suggestions on how to configure this.

 

 

 

 

Edited February 18, 2023 by chuga

[Vr2Io]

Pls note B is Byte and b is bit.

[chuga]

17 minutes ago, Vr2Io said:

Pls note B is Byte and b is bit.

I need to go back and see if I was comparing bytes to bits.  Wish they would pick one and be consistent when specing hardware. 

[Decto]

Hi,

 

The T400 has minimal requirements but likely a board of this age expects it in the top slot so it's fine there.

 

If it's recognised I would put the LSI in the x16 slot thats is x8 electrically  (shared with VGA), that will maximise the bandwith to the drives for a PCI-E 2 x8 card.

 

PCI-E 2.0 x1 is 500MBps while SATA 3.0 is 600MBps

As a rough rule, you can support ~2 modern SATA HDD per PCI-E lane, or 1 x SATA SSD without significant impact. 

X4 likely OK, X8 better.

SATA SSD are also prefered on the motherboard as I seem to remember Trim doesn't work fully on the old LSI SAS cards.

 

 

 

Edited February 18, 2023 by Decto
Added quote

[chuga]

2 hours ago, Decto said:

Hi,

 

The T400 has minimal requirements but likely a board of this age expects it in the top slot so it's fine there.

 

If it's recognised I would put the LSI in the x16 slot thats is x8 electrically  (shared with VGA), that will maximise the bandwith to the drives for a PCI-E 2 x8 card.

 

PCI-E 2.0 x1 is 500MBps while SATA 3.0 is 600MBps

As a rough rule, you can support ~2 modern SATA HDD per PCI-E lane, or 1 x SATA SSD without significant impact. 

X4 likely OK, X8 better.

SATA SSD are also prefered on the motherboard as I seem to remember Trim doesn't work fully on the old LSI SAS cards.

 

 

 

thanks.  I put the LSI in the x4 as the manual said if you put something in the x8 it will share with the x16 and they will both run at x8.  So not sure if that limits the t400

 

i know I am on borrowed time with the z68.  Who would have guessed 10 years running unraid on this board with no issues.. 

[Decto]

10 hours ago, chuga said:

thanks.  I put the LSI in the x4 as the manual said if you put something in the x8 it will share with the x16 and they will both run at x8.  So not sure if that limits the t400

 

i know I am on borrowed time with the z68.  Who would have guessed 10 years running unraid on this board with no issues.. 

 

Some testing I read a couple of years back showed 2-3% performance loss with a RTX 2080TI, RTX 3070 when using PCI-E 3.0 X8 vs X16.

The T400 has a fraction of the cuda cores (approx 7% of a RTX 3070) so there should be no bottleneck at x8 with rendering functions.

I assume the T400 will mostly be converting 4K to other formats so the maximum throughput for that has to be less than your HDD max transfer rate which is already exceeded by PCI-E 2.0 x1.

 

X4 on the LSI will work, though if you have it fully populated with higher performance drives, there may so capping of performance during parity verification or a rebuild.  

 

I have a GA-Z68X-UD3P-B3 I've owned from new, board still works great, ran it 24/7 for 12 months doing some crypto mining with spare GPU's recently with no issues at all. Now it's back to being a bench board as it's great for flashing other cards in etc, as it has a nice simple BIOS, none of this UEFI nonsense!

[chuga]

3 hours ago, Decto said:

 

Some testing I read a couple of years back showed 2-3% performance loss with a RTX 2080TI, RTX 3070 when using PCI-E 3.0 X8 vs X16.

The T400 has a fraction of the cuda cores (approx 7% of a RTX 3070) so there should be no bottleneck at x8 with rendering functions.

I assume the T400 will mostly be converting 4K to other formats so the maximum throughput for that has to be less than your HDD max transfer rate which is already exceeded by PCI-E 2.0 x1.

 

X4 on the LSI will work, though if you have it fully populated with higher performance drives, there may so capping of performance during parity verification or a rebuild.  

 

I have a GA-Z68X-UD3P-B3 I've owned from new, board still works great, ran it 24/7 for 12 months doing some crypto mining with spare GPU's recently with no issues at all. Now it's back to being a bench board as it's great for flashing other cards in etc, as it has a nice simple BIOS, none of this UEFI nonsense!

thanks, yes the T400 is for any transcoding (mainly via Emby) needs.

 

agree on the bios.  I hooked up a monitor to it for the first time in years to check the LSI firmware.   I went into the Z68 bios and it was a step back in time - only a few menus to go through.  keyboard control, etc.