12Gb/s and 6Gb/s Smart Array Controllers - Conflicting specifications? Limits?

[6BQ5]

The internet is notorious for providing confusing and conflicting information.!

I am looking for a Smart Array storage controller to install in my ML350p Gen8 server. The recommended controller models at the time the server was still current are:

• P420
• P421
• P430
• P431
• P822

I'd like to know for certain which controllers support 12Gb/s transfer rates and which ones support 6Gb/s transfer rates. Are they all 6Gb/s? 

I understand depending on the model these controllers provide 1 port, 2 ports, or 4 ports. If all of them only support 6Gb/s then are people simply multiplying the number of ports (i.e. 2) by 6Gb/s to get 12Gb/s?

Are other Smart Array controllers compatible with the ML350p Gen8? For example, could I use one that was released with the Gen9 servers? I'm afraid that HPE put something in the design to lock users out.

Thanks!

[sudhirsingh]

Hi,

Please refer ML350p Gen8 server quickspecs to know about all the supported Smart array controllers (page 42)

https://h20195.www2.hpe.com/v2/getdocument.aspx?docname=c04128239

You have outlined almost all of them, except - HP Smart Array P830 Controller.

 P430, P431 and P830 are capable of 12 Gb/s transfer rate.

You should refer Smart array controller quickspecs for more information.

However please refer "HP ProLiant Gen8 Smart Array Controllers datasheet" for details information about Gen8 smart array controllers, (i believe this will answer all your queries)

http://www.hp.com/hpinfo/newsroom/press_kits/2014/HPDiscover2014/HPProLiantGen8_DataSheet.pdf

•Internal ports 
– 1 x 4 mini–SAS (four total SAS 6 Gb/s physical links)===>One mini sas port support 4 drives
– 2 x 4 mini-SAS (eight total SAS 6 Gb/s physical links)===>Two mini sas port support 8 drives

– 1 x 8 double-wide (eight total SAS 12 Gb/s capable physical links)===>Single double-wide port support 8 drives

Gen9 Smart array controllers are not supported on Gen8 server,

Hope this helps!

Regards,

Sudhir

[6BQ5]

Hi Sudhir,

Thanks for the reply!

Let's take a deeper dive into the P430. According to the QuickSpecs, this card support 12 GB/s across one port.

The HPE Server Options Compatibility Tool shows the P430 as only supporting 6Gb/s across two ports.

Looking at this I thought the P430 card supports 6GB/s read and 6GB/s write speeds. Therefore, that would appear as a 12GB/s transfer speed.

The Smart Array Controller datasheet you sent me also simply says 12GB/s.

The Technical Specification Summary in the Smart Array Controller continues to list 12GB/s but with a footnote.

The footnote is a crystal clear and vague at the same time.

What infrastructure do I need? Do they mean that the Gen8 server in general supports 12Gb/s and all I need are 12Gb/s drives? Or do I need even more extra hardware beyond the P430 controller and 12Gb/s drives?

And one more instance. Take a look atthe online Specifications.

Does this mean the card supports 12Gb/s drives but the card can only transfer 6Gb/s from the drives to the rest of the system?

You're right - I did miss the P830 controller. It seems that card would be good for connecting to two drive cages. In that case I could disregard my internal P420i controller. Is installing two P430 cards to get the functionality of a single P830 allowed?

Thanks!

[6BQ5]

Replying to myself here and bubbing this thread back to the top ...

Hi Sudhir,

Did you have a chance to read my long reply? One of my questions was could I have more than one external Smart Array Controller installed in my ML350p? Would that be functionally equivilent to one P830 card? P430 cards are much more easily available and cheaper than P830 cards. I could install one P430 per processor to even out their placement.

Thanks!

[sudhirsingh]

Hi,

I believe except DL580 Gen8 non of the Gen8 servers support 12Gb link speed.

however few controllers (P430/P830) are capable of 12G speed which means these controller can support 12Gbps drives.

but the link speed will be 6Gbps.

P431 having 12Gb External port which can support 12Gb link speed if D3600/D3700 Disk enclosures are connected with correct Options.

Few observation:

P830 Quickspecs:

12 Gb/s SAS performance when used on a DL580 Gen8 with 12 Gb/s devices (HDD or SSD),
The P830 Controller supports up to 16 drives without expander; for example on a DL38x
Gen8 server that comes with 8 SFF drives can scale their internal storage by adding an
additional 8 SFF drive cage connected to Smart Array P830

P430 Quickspecs:
12Gb/s SAS performance when used on a DL580 Gen8 with 12Gb/s devices (SSDs or HDDs)

DL380p Gen8 Quickspecs:

NOTE: All 12G SAS Hard drives only operate at 6G speeds in the DL380pGen8.

You can use 2xP430 controller in the server, (Connect one 8SFF backplane to one P430)

P830 can support 16 drives wihtout expander.

HP ProLiant ML350p Generation 8 (Gen8) Quickspecs:
NOTE: The HP Smart Array P430 controller is not supported in Slots 3 and 4

also, please check the cable options and cabling diagram before adding additional controller/backplane.

Hope this answer all your queries!

Regards,

Sudhir

[6BQ5]

Hi Sudhir,

Thanks for the detailed response! There's a lot of information in your reply but there is one item I need to pick apart with you.

---

@sudhirsingh wrote:

I believe except DL580 Gen8 non of the Gen8 servers support 12Gb link speed.

however few controllers (P430/P830) are capable of 12G speed which means these controller can support 12Gbps drives.

but the link speed will be 6Gbps.

Whoa! That's a bombshell. I understand the integrated Smart Array Controller in the ML350p Gen8, the P420i, is a 6 Gb/s device by design. Are you saying that if I install a P430 into one of my PCie slots and connect it to a SFF cage full of 12 Gb/s drives I will only see effective speeds of 6 Gb/s due to a design limitation of the ML350p Gen8 server itself? I find it hard to believe that HP would limit their flagship tower server to 6 Gb/s transfer speed.

@sudhirsingh wrote:

HP ProLiant ML350p Generation 8 (Gen8) Quickspecs:
NOTE: The HP Smart Array P430 controller is not supported in Slots 3 and 4

---

Is there anything to prevent me from using slots 2 and 5? I'm still planning (hoping?) to install GPU cards in slots 3 and 6 (or 8).

@sudhirsingh wrote:

Hope this answer all your queries!

Not yet, but getting closer!

Thanks!

[sudhirsingh]

Hello Boris,

• Both 12G supported adapter (P430 and P830) for ML350 Gen8  has written following in their quickspecs

           "12Gb/s SAS performance when used on a DL580 Gen8 with 12Gb/s devices" 

            also

           All 12G SAS Hard drives only operate at 6G speeds (per DL380pGen8 quickspecs)

• P430 in Slot 2/slot 5 should be fine,
• Seems to be design limitation, it was launch in 2012 with 6Gb options only ,12G support/options added in 2014.
• Same year Gen9 was launched which supports SAS 12G link speed.

Hope it clarifies !

Regards,

Sudhir

[6BQ5]

Hi Sudhir,

Alright then ... it looks like the ML350p Gen8 server will only see 6 Gb/s performance regardless of whatever Smart Array controller is ued. Only the DL580 server will push data through at 12 Gb/s.

Sorry it took me a while to get my head wrapped around that.

But, thanks for your patience!

[sudhirsingh]

You are welcome Boris,

If you feel this was helpful please click the KUDOS! thumb below!   

Regards,

Sudhir

[DanRobinson]

Not sure it's ever made clear in this (rather long) thread.

The Drive Cage Backplane has to support the speed you want, along with the controller.

The DL580 Gen8 came out much later than the others (DL380, ML350, etc) and so it's drive cages all support 12G.

But dropping a P430 into a ML350 means the drive cage is now the bottleneck and causes the drives to be only 6G capable.

FYI, the P430 is effectively a P440 Gen9 controller that was backported to Gen8.
So even though the Link Speed may be limited to 6G, the RAID 5/6 speed of the P430 should me much faster than the P420 due to it's use of the faster ASIC under the hood.

Lastly, if you use Spinning Rust, the 6G speed will always be faster than the drive can sustain anyway, beyond the initial cache hits from the RAM on the drive.  Fastest spinning drives only ever hit 250MB/s.
So it's only SSDs where this becomes an issue at all.

[6BQ5]

Hi @DanRobinson !!

Not sure it's ever made clear in this (rather long) thread.

The Drive Cage Backplane has to support the speed you want, along with the controller.

The DL580 Gen8 came out much later than the others (DL380, ML350, etc) and so it's drive cages all support 12G.

But dropping a P430 into a ML350 means the drive cage is now the bottleneck and causes the drives to be only 6G capable.

[Underline and bold is my emphasis]

Wow, I never would have thought that the drive cage is the limiting factor in transfer speeds! So I can get a P430 or a P420 external card and I could use 12G or 6G drives ... my maximum theoretical transfer speed is only going to be 6Gb/s on my ML350p Gen8 machine.

On the one hand, I'm a little disappointed because I really wanted that extra speed. However, on the other hand, I'm relieved because it's one less thing for me to worry about. I'm just going to have 6Gb/s speed so I can move on to other things.

I did notice when playing with RAID 0 arrays I did not get faster performance after going beyond two drives. Going to three drives and beyond made no difference. I probably reached the transfer speed limit of the cage.

FYI, the P430 is effectively a P440 Gen9 controller that was backported to Gen8.
So even though the Link Speed may be limited to 6G, the RAID 5/6 speed of the P430 should me much faster than the P420 due to it's use of the faster ASIC under the hood.

Lastly, if you use Spinning Rust, the 6G speed will always be faster than the drive can sustain anyway, beyond the initial cache hits from the RAM on the drive.  Fastest spinning drives only ever hit 250MB/s.
So it's only SSDs where this becomes an issue at all.

"Spinning Rust" almost has a romantic ring to it! Yes, I am using good old fashioned spinning drives in my project. This is another case of being saddened by the limit but relieved that I shouldn't worry about what I can't change. Just keep building.

Thanks again for this info!