Microchip Adaptec 24G SAS Tri-Mode RAID and HBA Launch

zir_blazer

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Dec 5, 2016
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No info on prices? Not expecting them to be cheap, but seems like a powerful swiss knife. Serves the purpose of a PCIe Switch plus SAS and SATA support.

Also, since NVMe is just a protocol build on top of PCIe, I wonder if it can be used as an actual PCIe Switch to plug arbitrary PCIe Devices on the other end. Far more interesing than PLX/Avago expensive PCIe Switches. If the price is competitive and not being a pure PCIe Switch doesn't add major overhead or compatibility issues, I would love to use these as some sort of generic fanout adapter.
 

funkywizard

mmm.... bandwidth.
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An hba might be simple enough to be a raw pcie switch if they wanted to do that. Probably not well suited to that purpose but hypothetically possible.

A raid card on the other hand obscures from the OS as to what drives are connected, presenting the OS with a virtual drive for each array. In turn, talks to the underlying storage and accelerates raid mirroring and parity, and provides writeback caching (essential for parity raid levels like raid 5 to ensure adequate latency write commits). This also helps with bus oversubscription -- a write to a raid 1 only requires 1 write over the pcie bus but 2 writes to the attached drive so when the raid card does this multiplexing you use less pcie bus bandwidth. This kind of product would be inappropriate to act as a raw pcie switch -- just very far outside what it's designed for.
 

zir_blazer

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As far that I know, the HBA and RAID cards may use the same silicon but with different Firmware (IT/IR Modes), so it doesn't necesarrily disqualify RAID cards from being able to be used like that, either. Yeah, you're telling it "ignore the onboard battery and RAM and go completely dumb", but that may also be viable. Also, the brochures for some of the TriMode controllers (Not only Microchip, but other brands too) usually mentions "integrated PCIe Switch" (Which makes sense, it is mandatory for a NVMe HBA) but no one mentions specifically my use case AS a PCIe Switch.

For reference, what I'm looking at is at things like this PCIe 16x-to-8 OCuLink adapter that uses a PCIe Switch (That cost around 300-350 U$D), which could be made potentially obsolete if the new TriMode adapters could also serve the purpose of dumb PCIe Switchs, assuming than the price isn't much higher and there aren't other major cons.
 

funkywizard

mmm.... bandwidth.
Jan 15, 2017
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As far that I know, the HBA and RAID cards may use the same silicon but with different Firmware (IT/IR Modes), so it doesn't necesarrily disqualify RAID cards from being able to be used like that, either. Yeah, you're telling it "ignore the onboard battery and RAM and go completely dumb", but that may also be viable. Also, the brochures for some of the TriMode controllers (Not only Microchip, but other brands too) usually mentions "integrated PCIe Switch" (Which makes sense, it is mandatory for a NVMe HBA) but no one mentions specifically my use case AS a PCIe Switch.

For reference, what I'm looking at is at things like this PCIe 16x-to-8 OCuLink adapter that uses a PCIe Switch (That cost around 300-350 U$D), which could be made potentially obsolete if the new TriMode adapters could also serve the purpose of dumb PCIe Switchs, assuming than the price isn't much higher and there aren't other major cons.
Looking at similar Brocade adapters, 16i hba runs $700-800, and the raid card well over $1000.

So if a pcie switch card runs 300 bucks yeah theres zero reason to use an hba or raid card for that function.
 

zir_blazer

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So if a pcie switch card runs 300 bucks yeah theres zero reason to use an hba or raid card for that function.
Do note than the card I posted is an already old PCIe 3.0, a 4.0 one with a current generation PCIe Switch will certainly be significantly more expensive than that, reducing the pricing difference.

I'm not sure about prices to make a proper comparison for how much extra you would have to pay, and we're already assuming than the TriMode HBAs actually work as standard PCIe Switches. I'm just mentioning such possibility, than if that is true and stars aligns so that the pricing is small enough to be considered, it may also be a better option.
 
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