Beginning PCIe RAID

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NExUS1g

Gawd
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Aug 15, 2004
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In order to not be capped by the motherboard bus, I'm looking at purchasing a PCIe RAID adapter. Something along the lines of http://www.newegg.com/Product/Product.aspx?Item=N82E16816151122. I'm planning on setting up several http://www.newegg.com/Product/Product.aspx?Item=N82E16820147359 in RAID 0 (128 GB per drive to a total of about 1TB, perhaps more, total single volume space -- 6, 7 or 8 drives total, about).

What's the maximum data bandwidth supported by a SAS/mini-SAS connection?

Can it only support bandwidth from a single SSD per mini-SAS/SAS port?

I think that 8 PCIe lanes would provide more bandwidth than I could reasonably RAID to one slot (16GB/s -- 8GB/s each for up and down -- if I my knowledge is accurate), but is there a feasible limit I could easily cap myself on if I'm not careful?

How much memory would be recommended on the card itself for this number of drives and setup and why?

Is there anything else I need to consider as well?
 
For this setup, I'm not interested in redundancy, but purely performance for simultaneous access on a large scale. There will be daily backups to an offsite RAID 1 storage for security of data, and the interim data between those updates that may be lost in the case of a catastrophic failure or disaster isn't going to be "mission critical" type stuff.

Will 2 mini-SAS connectors be capable of supporting up to 8 6.0Gb/s SSDs?
 
A single miniSAS connection is basically 4 separate SAS connections unless connected to a SAS expander. Thus, it can drive 4 drives at full speed.

However, the ix-Areca controllers already contain an expander. I remember that all the internal ports are driven by a single wide SAS port (x4) while the second wide SAS port goes to the external port. The controller itself only has two wide ports. This means that all internal ports together are limited to 24 Gbps or 3 GB/s.

I would get a 9271-8i controller with FastPath and a CacheVault module for maximum performance.
 
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NExUS1g said:
What's the maximum data bandwidth supported by a SAS/mini-SAS connection?
Can it only support bandwidth from a single SSD per mini-SAS/SAS port?
Click to expand...

each sas connector supports 4 drives with a breakout cable, and the transfer rate on that card is "Up to 6Gb/s" ... so it'a sata3 spec, which means up to 600 MB/s per channel, or ~2.4GB per sas port max..


NExUS1g said:
I think that 8 PCIe lanes would provide more bandwidth than I could reasonably RAID to one slot (16GB/s -- 8GB/s each for up and down -- if I my knowledge is accurate), but is there a feasible limit I could easily cap myself on if I'm not careful?
Click to expand...

if you have a pcie3 motherboard, you can use 16 of those 850pros before worrying about saturating the pcie bus, but if your mobo is pcie2, 8 could be hitting the limits but only in best case scenario
 
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