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I am researching making a DIY SAS array much like the Dell MD1000. My understanding is that these devices do not contain a RAID controller, instead they present all the drives on in SAS domain to the host.

I would like to build the same type of array. The MD1000 and all similar devices contain built-in SAS expanders in order to present more than 4 drives to the host via a single cable.

My question is, what SAS expanders are they using? The only expanders I can find are PCI cards, which must be attached to a motherboard. Will my JBOD array require a motherboard, or are there stand-alone (i.e. dumb) SAS expanders that function independently of a motherboard?

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Why are you trying the DIY approach versus a purpose-built solution? –  ewwhite Jan 9 '12 at 13:05
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Poor man's bleeding edge? The MD1200 is going to cost him around 3 thousand dollars without drives. –  the-wabbit Jan 9 '12 at 13:58
    
If this is for personal use or fun, it doesn't belong here. If it's for business, you're spending more money and time trying to reinvent a wheel that's been thoroughly invented many times. Dell is the example you've given, but there are thousands of companies that make (and warranty) little storage enclosures. –  Basil Jan 9 '12 at 14:55
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A "playground" is not necessarily personal use or fun - it might be used for prototyping or as a necessary part for a proof-of-concept where you neither have the budget nor the need for a fully-warranted solution. –  the-wabbit Jan 9 '12 at 16:56

4 Answers 4

up vote 3 down vote accepted

I do not know about the MD1000, but probably they will be using some custom-made PCBs to have an expander run without a mainboard.

The SAS expanders usually will need the mainboard / PCIe slot for power supply only, so theoretically, you could use any mainboard, even without a CPU. There is this rather well documented DIY-JBOD project where an industrial PCIe PCMIG backplane (originally used for slotting SBCs but obviously providing power to any PCIe card) has been used instead of a full board:

PCMIG backplane

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I would look on a HP sas expander, works great

Q: How do I install the HP SAS Expander and what are the power requirements?

A: The card needs an x4 PCIe slot on a motherboard and draws 11 watts of power. The card doesn't require software drivers, it is invisible to the operating system and motherboard. A common dilemma is people needing to use this card in an empty chassis like a Norco RPC-4220 to create a JBOD enclosure. Some people have resorted to using an old motherboard serve as a power source and ON/OFF switch for the chassis - such a solution costs significantly less than buying a prefab expander chassis. Unfortunately this card has no external 4-pin Molex power connector like the Intel RES2SV240, another highly recommended SAS expander card, but in exchange you're getting 36 ports instead of 24 on the Intel

Source: http://hardforum.com/showthread.php?t=1484614

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Does the motherboard require a CPU and memory installed? i.e. is the purpose of the mother board solely to draw power, or does the expander require the CPU and memory to offload functionality. –  Jacob Groundwater Jan 9 '12 at 11:35
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No, you would not need CPU or memory on the mainboard. Check out the link to the project at servethehome.com in my response where the HP SAS controller has been used as well. –  the-wabbit Jan 9 '12 at 11:50

I've just put together a chenbro RM31616 setup which uses a sas expander linked to an LSI raid card. The sas expander is pci form factor but uses the pci slot just for physical stability, ie, all the motherboard interfacing is done via the raid card.

I don't know if that helps you at all.

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I would like to create a JBOD array that is entirely separate from the eventual computer it will attach to. Are you using the same motherboard to power the expander as to interface with the RAID card? –  Jacob Groundwater Jan 9 '12 at 11:37
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kind of. The sas card takes a normal psu 4 pin plug, and connects to the raid card. It dosent actually connect to the motherboard at all, but just sits in a pci slot for stability. –  Sirex Jan 9 '12 at 12:18
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+1 For DIY storage this the Chenbro line of SAS Expanders are the way to go. They also offer a kit to install the card in the motherboard windows of a standard ATX case, fan and error light controllers, etc. –  Chris S Jan 9 '12 at 15:01
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one handy tip for the RM31616, make sure the sas cables you get have a small distance before they can be bent, else you'll foul on the internal fans, as i found out this morning. Otherwise its a good setup. –  Sirex Jan 9 '12 at 15:52

Some of these drive bay assemblies from Supermicro come with expanders built-in. You might get what you want from those.

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