SAS Recommendation, LSI 16i or Extender?


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Hi,

 

Hoping to get the attention of @johnnie.black ;-) 

 

I have just purchased an X-Case 4U with 24 Hot Swappable Bays and it has a backplane with 6 SAS Connectors.

 

https://www.xcase.co.uk/collections/4u-rackmount-cases/products/x-case-extra-value-rm-424-24-hotswap-bays

 

image.png.032a7e16e1b1ec83831379668d654fce.png

 

I am running an ASUS Maximus V FORUMULA and here are my options and what hardware I have

 

LSI 2008 8i for 2 of the ports on the backplane

Unicaca 3008 8i for another 2

2 X Reverse Breakout Cables for the 6XSATA 3 Motherboard Connectors & 2XSATA 2 Motherboard Connectors.  (Not sure if connecting a reverse breakout cable to 2 SATA3 and 2 SATA2 will be an issue?

 

I would like to either upgrade the LSI 2008 8i for a 16i or get a SAS Expander for the Unicaca 3008.  The cost is about £80 more to go the 16i route but not sure if it is beneficial in any way?

 

Any input/guidance is REALLY appreciated as always 🙂

 

 

Edited by mbc0
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22 minutes ago, mbc0 said:

(Not sure if connecting a reverse breakout cable to 2 SATA3 and 2 SATA2 will be an issue?

Not a problem.

 

The Expander + 3008 would provide more bandwidth than a 2008 16i, but current config, using the onboard SATA ports, will perform just as well, assuming both HBAs are on CPU slots.

 

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Hi @johnnie.black Many thanks for such a quick reply!

 

The PCI/CPU section is where I get a bit confused.

 

I have 3 PCI-E X16 Slots and need to use the following cards

 

SAS 3008 PCI-E X8

SAS 2008 PCI-E X8

10gbE Card PCI-E X8

 

Here is what my motherboard manual says (I am running an i7-3770k) 

 

Does it basically mean if I put the SAS3008 in Slot 1 it will run at 8X but at the cost of  Slot 2 & 3 running at X4?

 

image.png.4aae21ea88f28ce99ab5eba07c454258.png

 

image.thumb.png.48b3f8b7733afa8f8c7e64372feb7abf.png

 

image.thumb.png.957132b54688f8c1fc1d9ac79fec8bc2.png

 

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Thanks for your time Johnnie, I really appreciate it!

 

Final question!

 

With the bottleneck I am facing by using 3 cards on my Motherboard where would I stand with performance using this config or getting an expander?

 

🙂 

Edited by mbc0
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Thanks @johnnie.black but I am not sure I am with you?

 

I cannot justify the cost of a SAS3 expander, so what I was trying to understand is would it be best to have the system running SAS3008 X8, SAS2008 X4 and Reverse Breakouts SATA to SAS or SAS3008 with a SAS2 Expander (RES2SV240) ?

 

Thank you again and sorry if I am too stupid to understand!

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4400 / 16 = 275MB/s vs the approximately 190MB/s max with the SAS2008 on a x4 slot, question is are your disks faster than that? You didn't mention what disks you have, say for example you have 4TB WD Reds, they max out at around 175MB/s, so either option would be the same, if you have faster disks or want to have some spare bandwidth for future upgrades then get an expander.

 

 

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Thanks Johnnie, I understand... I currently only have 2 12gb/s SAS Drives, 1TB SSD Cache drive amd a Barracuda Pro but the rest are just mediocre Toshiba's, Samsungs & Seagates so nothing blistering fast!

 

Every drive I get from now will be a 12gb/s SAS drive but it will take a very long time to fill so I think I will use the config I originally stated until I have enough disks to warrant upgrading to SAS3.

 

Again, you have been so helpful, Massive Thanks!

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  • 4 weeks later...

Hi @johnnie.black

 

Sorry to bother you again but I have had quite an upgrade since last speaking to you regarding my SAS controllers,

 

I am nos using 

 

M/B: Gigabyte Technology Co., Ltd. - X399 DESIGNARE EX-CF

CPU: AMD Ryzen Threadripper 2950X 16-Core @ 3700

 

so I have 5 PCI-e lanes and would like to know wether or not running 2 SAS Controllers for 16 disks would give any performance benefit over a SAS 12GB controller with a RES2SV240?

 

Thanks as always!

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yes, sorry I meant slots!  

 

Ok, thank you, that is what I thought, I use SSD's on the SATA ports and it will be many years away before I get disks fast enough to bottleneck the RES2SV240 so I am going to go ahead and order one leaving the slots spare for VM's maybe ;-)

 

Thanks so much as always for your support Johnnie!!

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  • 4 weeks later...

I'm sorry, I need to ask an advice, I'm planning an Unraid server and I was looking after an Intel RES2SV240 expander

 

the plan is to use only 2.5"" HDD to keep noise as low as possible.

 

https://www.seagate.com/www-content/product-content/barracuda-fam/barracuda-new/files/barracuda-2-5-final-ds1907-1-1609gb.pdf

 

looking at the Seagate drive spec they state max transfer is up to 140MB, could it be an option to use one 3008 HBA with 2xRES2SV240 connected to the same board?

If I have correctly understood each 3008 can provide 4400MB of bandwidth with a SAS2 expander so if I split it on two boards I should receive the following data

2200/16=137.5 MB/s each drive

2200/20=110 MB/s each drive

 

these drives will be used for purely bulk storage of video/music/camera recording, if some VM will need dedicated drives the MB has ports that could be used.

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13 minutes ago, Melandir said:

2200/16=137.5 MB/s each drive

2200/20=110 MB/s each drive

That's correct (a SAS2 HBA would also provide the same bandwidth), note that those disks are SMR, and while it should't make much difference for typical Unraid use it's good to be aware.

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Thanks Johnnie

 

do you have an example of SAS2 HBA (SAS2008 maybe)? just to check the price difference on the used market, if it's not that much I'll probably stick with the SAS3 HBS so in the future I can upgrade to a SAS3 expander to increase the bandwidth available and the disk count

 

I have an old IBM M1015 that I flashed to LSI to play with Freenas and never used it again is it useful?

Edited by Melandir
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Thanks Johnnie,

 

another question please, searching the internet I found that HP 24 Bay sas expander are cheaper than Intel ones (RES2SV240) and I don't understand completly the difference between them, the only big difference I have been able to spot is that Intel expander can be powered without connecting it to the PCIex slot, do you know if that is the only one or there are other difference and maybe the Hp cards does not work well in Unraid?

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5 minutes ago, Melandir said:

do you know if that is the only one or there are other difference and maybe the Hp cards does not work well in Unraid?

It does work with Unraid, I have one myself, besides the power thing they are SAS2/SATA2, the Intel is SAS2/SATA3, so with SATA drives bandwidth will be cut in half, so 1200MB/s per link (1100MB/s usable).

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I was expecting that the single drive will be limited to SATA2 speed (more than enough with standard HDD) not that the entire card will receive half the bandwidth :(, in my case Intel expander looks still be best with price/performance/space (does not take a PCIex slot) ratio around, with my config each drive will be limited to 55MB/s with a 20 Drive configuration.

 

I have lots to learn in this field

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4 minutes ago, Melandir said:

I was expecting that the single drive will be limited to SATA2 speed (more than enough with standard HDD) not that the entire card will receive half the bandwidth :(

Yes, the link between the expander and the HBA is based on the link speed of the devices, each link has 4 lanes, so it's 4 x disk link speed. LSI SAS3 HBAs and expanders get around this with Databolt technology, where you can get close to full SAS3 bandwidth when using SAS2/SATA3 devices, more info here:

 

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