How PCIe channels affect SATA port multipliers

[segaboys]

First post, hope I make sense, I have spent alot of time trying to find the answer on the forum and have finally resort to asking the question.

Thanks in advance.

 

All the forum posts I have read have pointed me towards using PCI-E ahead of the cheaper PCI SATA controllers for adding more SATA ports to my UnRaid Server.

The motherboard I have - ASUS P5e-VM DO - has six sata ports and 1 x PCIe x16 port  and 1 x PCIe x1 port.

I also have 3x X-Case 5in3 Drive storage kits with 5 Sata connectors on the back each making the machine host 15 Disks in total.

 

I have been trying to find the most cost effective way to move past the 6 SATA ports and to at least 15 ports.

Understanding all I have read I really need to find a card able to control the hard drives I add and it does not require RAID ability as that is not used by unRAID.

The ideal solution would be a 20port SATA controller without RAID on a x16 PCIe card or a motherboard supporting supporting 20 harddrives using SAS cables and as these don't seem to exist I have looked into the following.

 

I have limited options with PCIe ports on my motherboard so I need to buy right the first time and I have been looking at the following cards on ebay:-

 

STLab PCIex4 with 4x internal SATA connectors @ £62http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=110581200352&ssPageName=STRK:MEWAX:IT

•Bus Interface: PCI-Express x 4

•Marvell 88SX7042 chipset

•Compliant with PCI Express Base Specification 1.0a

•Compliant with Serial ATA 1.0 specification with support for full complement of SATA II optional features

•Supports SATA II Native Command Queuing (NCQ)

•Provides four independent channels to support up to four Serial ATA drives

•Supports SATA up to 300MB/Sec

•4 x internal SATA connectors

•2 x external eSATA connectors

 

PCIex1 with 4x internal SATA connectors @£42 http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=280504574483&ssPageName=STRK:MEWAX:IT

•Provides 4 x SATA port (internal) for SATA Hard Disk

•1-Lane (x1) PCI-Express with transfer rate 2.5 Gb/s Full Duplex channel

•Compliant with PCI Express Specification Revision 1.0a

•Compliant with Serial ATA II Specification

•Compliant with Gen2i, Gen2m SATA II Electrical Specification Revision 1.0

•Data transfer rate up to 3.0Gb/s

•Backward compatible to SATA 1.0 Specification

•Support Native Command Queue (NCQ), FIS Based Switching with Port Multiplier

•Support 4-independent SATA channels

•All external ports are compatible to eSATA Specification

 

 

Leaf - Silicon Image PCIex1 with 4x internal SATA connectors  @ £60  http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=290454191057&ssPageName=STRK:MEWAX:IT

•4 Port Sata II 300MB/s

•PCI Express x1, works also in PCI Express x4 and x8 Slots

•supports 4 internal HDD, as WD Green Caviar 4x2TB or seagate ST31500341AS 4x1.5TB or 4 external HDD using LC4CEB eSATA Adapter

•with own Bios (works independent from OS)

•supports Portmultiplier for up to 20 HDD

 

My questions are as follows:-

 

1. Assuming compatibility with UnRaid, does it matter if the PCIe cards are x4 or x1 as it does not seem reduce the amount of independant channels per drive?

 

2. If I were to choose to use a port multiplier to reach the 15 drive enclosure limit or the 20 drive license limit, I assume it then splits the channel bandwidth accross the multiplied ports and as the second card has a data transfer rate of 3.0Gb/s running on a x1 PCIe port @ 2.5Gb/s is that 2.5Gb/s divided by the amount of ports multiplied to?

 

3. Or is it that with SATA II @ 300MB/s you could effectively multiply a port by the amount bandwidth you have on the lane so a 2.5Gb/s PCIe lane  can multiply to 8.3 SATA II ports and therfore a PCIe x1 port could support 8 x SATA II drives through port multiplication

 

I have probably assumed alot of of things incorrectly - I am really trying to find out how, PCIe multiplication map to lanes, how lanes map to ports, how port multiplication impacts port bandwidths.

 

Thanks for any help.

[Rajahal]

I don't know how hard it will be to find these outside of the US, but this is your best option:

 

SUPERMICRO AOC-SASLP-MV8 PCI Express x4 Low Profile SAS SAS RAID Controller

+

3ware CBL-SFF8087OCF-05M 1 unit of 0.5m Multi-lane Internal (SFF-8087) Serial ATA breakout cable, forward x 2

+

SATA2 Serial ATA II PCI-Express RAID Controller Card (Silicon Image SIL3132)

 

After these two cards, you would have a total of 16 SATA ports (6+8+2), all operating at full speed, no bottlenecks.  Note that you will need two breakout cables (as well as some standard SATA cables).  Make sure that you get Forward breakout cables, only they will work for this setup.

 

The PCIe x4 or faster port is capable of running 8 SATA drives simultaneously at full speed.  At PCIe x1 port is capable of running only 2 SATA drives simultaneously at full speed.  If you try to run more than these limits, you will see some performance hits.

[segaboys]

Thank you very much for the help, I will try and track them down in the UK.

[GK20]

1. Assuming compatibility with UnRaid, does it matter if the PCIe cards are x4 or x1 as it does not seem reduce the amount of independant channels per drive?

 

4X has more throughput than 1X. 16Gb/sec vs 4Gb/sec (per PCIe-2.0, for old PCIe-1.0 cut those numbers in half). Assuming (yes it is not going to happen) your disk really can pump data at SATA-2 rate (3 Gb/sec), one disk can almost saturate your 1X PCIe card.

 

2. If I were to choose to use a port multiplier to reach the 15 drive enclosure limit or the 20 drive license limit, I assume it then splits the channel bandwidth accross the multiplied ports and as the second card has a data transfer rate of 3.0Gb/s running on a x1 PCIe port @ 2.5Gb/s is that 2.5Gb/s divided by the amount of ports multiplied to?

 

3. Or is it that with SATA II @ 300MB/s you could effectively multiply a port by the amount bandwidth you have on the lane so a 2.5Gb/s PCIe lane  can multiply to 8.3 SATA II ports and therfore a PCIe x1 port could support 8 x SATA II drives through port multiplication

 

The answer is "it depends" because the bottleneck in port multiplier is the host adapter that port multiplier connected to. If your port multiplier is connected to another SATA card through a SATA cable then most likely 3Gb/sec is what you get. if however port multiplier and SATA are integrated together in ONE card and this card has PCI-e 4X interface then you probably will get up to 6Gb/sec.

 

 

http://www.serialata.org/technology/port_multipliers.asp

 

 

[BRiT]

Several corrections need to be made.

 

A single lane 1x PCI-Express has 250 MB/s bandwidth.

 

Rework your math.

[GK20]

Several corrections need to be made.

 

A single lane 1x PCI-Express has 250 MB/s bandwidth.

 

Rework your math.

 

 

The PCIe 2.0 standard doubles the per-lane throughput from the PCIe 1.0 standard's 250 MB/s to 500 MB/s.

 

http://en.wikipedia.org/wiki/PCI_Express

[BRiT]

Yes, but which motherboards and which controller cards actually provide PCI-Express 2.0? 

 

The last time I examined this, on the motherboard side only the 16x slot provided for PCI-Express 2.0 and on the controller side only graphic cards used it. I'd love for the situation to have changed since then.

[GK20]

Yes, but which motherboards and which controller cards actually provide PCI-Express 2.0?  

 

The last time I examined this, on the motherboard side only the 16x slot provided for PCI-Express 2.0 and on the controller side only graphic cards used it. I'd love for the situation to have changed since then.

 

For MB if you look for something like P55 north bridge with LGA 1156 you will have a PCI-e 2.0 slot, even the old G41/P43 north bridges have it. The slot used for graphic card could be used for others as well in most of case, some vendors might have its limitation. in unRAID, video card slot is a perfect candidate for add-on SATA card.

 

http://www.newegg.com/Product/Product.aspx?Item=N82E16813121388

http://www.newegg.com/Product/Product.aspx?Item=N82E16813128388

http://www.newegg.com/Product/Product.aspx?Item=N82E16813130185&cm_re=neo3-f-_-13-130-185-_-Product

 

 

For controller, well, we know they are all slowly catching up but there are still some in the market like this one

http://www.tweaktown.com/reviews/3309/highpoint_rocketraid_640_sata_6gb_s_4_port_pci_e_2_0_controller/index.html

 

 

If you look at block diagram from Intel for Core-2 generation, They do put 500MB/sec for each 1X in south bridge.

http://lime-technology.com/forum/index.php?topic=3382.msg76967#msg76967

 

[segaboys]

I have gone through the Datasheet for the Q35 chipset on my motherboard.

The x16 PCI express port is compliant to the 1.1 Specification Revision and therefore operates at a frequency of 2.5Gb/s on each lane supporting a maximum theoretical bandwidth of 40Gb/s in each direction.

 

Raw bit-rate on the datapins of 2.5 Gb/s, resulting in the real bandwidth per pair of 250MB/s given the encoding used to transmit data accross the interface.

 

The maximum theoretical realized bandwidth on the interface of 4GB/s in each direction simultaneously, for an aggregate of 8GB/s when x16.

The bit that follows in blue is my deductions based on my understanding of what was said before.

So if I ran a x4 PCIe card in the slot it would run 10 Gb/s in each direction theoretically.However the maximum realized bandwidth on the interface would then be 1GB/s in each direction simultaneously, giving an agregate of 2GB/s. Each lane would still support 250MB/s but I would only have 4 in total. So the optimum would be 4 x SATA II Hard disks @ 300MB/s each. If I ran 8 @300MB/s it would be more than the bandwidth allows. As I rarely see my transfers to UnRaid pass the 55MB/s rate, I would assume 8 drives on a 4x controller is unlikely to cause a bottleneck

 

Appologies if I am covering old ground, its just that I am trying to understand it completely and prevent myself from sounding stupid in these forums in the future.

I suppose the killer question is does the x16 slot support anything other than a graphics card . I guess the only way I find out is if I stick one in there.

[GK20]

I suppose the killer question is does the x16 slot support anything other than a graphics card . I guess the only way I find out is if I stick one in there.

 

OR send the vendor an email asking tech support if this is feasible. It usually shouldn't be a problem but some users in here did report before having issues using this slot with anything other than video card, i am using Supermicro AOC-SASLP-MV8 in my 16X video card slot on my MSI MB without any problems.

 

 

[MrGrumpie]

segaboys, scan and x-case in the UK sell the supermicro board - scan are out of stock so I paid a premium and ordered from supermicro

[Kode]

Actually scan are showing in stock http://www.scan.co.uk/Product.aspx?WebProductID=1086873&source=froogle

 

Also when i ordered my supermicro motherboard it was a pre-order item only, and it still took less than a week to arrive.

[MrGrumpie]

Crap, I just paid £117 for mine!

[Kode]

Lol, sorry, pretend i didn't say anything

[MrGrumpie]

Lol, sorry, pretend i didn't say anything

I just managed to cancel the order with X-Case, now ordered from Scan so thanks!  £26 is too big a difference to ignore!

[Kode]

No worries

[segaboys]

The good news, my x16 port accepts x4 raid cards, I tested it out last night with a x4 adaptec card.

So as soon as I get the funds I will get the supermicro.