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Delta9
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Hypothetical Device to use NVMe storage to old PCs

Wed Jan 10, 2018 9:14 pm

Today after reading about the new x4 m2 NVMe drives I began to think about how a single drive with these performance capabilities could be used in old or aging PCs. I know that sticking a regular or multiple sata drives would be easiest but costley and held back by the older sata interface. I then considered PCIE cards with m2 drives onboard, however they require bios hooks to work. What I considered next is pure fantasy, a PCIE/PCI card or 2.5" form factor with a NVME drive onboard that can accept multiple SATA connectors to fool older mobos into thinking its a 2-4 drive raid 0 array. That way it only needs power from the expansion slot/psu, there aren't 4 drives with 2 cables each floating around, and the card/drive would manage functions that aren't supported by older boards in raid, like trim, ect. Is something like this feasible, or would it be a big, expensive engineering nightmare with few takers. Thoughts about how dumb of an idea this is?
 
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Re: Hypothetical Device to use NVMe storage to old PCs

Wed Jan 10, 2018 10:42 pm

Edit: I think I misunderstood what the OP was proposing. See my second reply (several posts down).

Well, if it's an older PC it's gonna be PCIe 1.0 or 2.0, which means an x1 slot isn't going to give you bandwidth that's meaningfully better than a SATA interface. So to get a worthwhile benefit, you'd need to use the x16 slot (hopefully the motherboard has a second one if the primary one is already occupied by a GPU).

IMO it's not an entirely stupid idea, but I doubt you'd have enough takers to make it more than a very low-volume niche product.
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Kougar
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Re: Hypothetical Device to use NVMe storage to old PCs

Wed Jan 10, 2018 11:06 pm

Expensive engineering nightmare. Where is the advantage to this over just building a regular RAID array? Low latency, TRIM, NVMe, and low overhead will be lost piping stuff through an abstraction layer and recombining it onto the card, and it would still require a RAID controller with its drawbacks.

You can stick PCIe-based storage onto older systems, the only catch is if you go back to X58 and P67 era hardware and older they will not be OS bootable. But you could still use them for programs with the OS on an old SSD or something.

To be honest, my advice to anyone wanting to keep an old computer around was to generally to find a SF-1200 controller SSD. Half a dozen companies made drives from them. They are worthless because they cannot be used on Z97 and newer chipsets, but they offer decent performance and make for a good, cheap upgrade. I stuck my old Vertex 2 SSD in my father's rig, was still a nice improvement over the spinning rust it used.
 
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Re: Hypothetical Device to use NVMe storage to old PCs

Wed Jan 10, 2018 11:34 pm

Why can't those particular drives be used on newer chipsets?
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Re: Hypothetical Device to use NVMe storage to old PCs

Thu Jan 11, 2018 2:34 am

Intel began prohibiting them because first-gen Sandforce controller SSDs didn't fully implement the entire SATA specification. OCZ, Corsair, Seagate, Mushkin, and ADATA are just some of the manufacturers that made SSDs with them.

My memory is fuzzy as Z87 chipsets had issues with first-gen sandforce controllers so I don't know for sure if Intel retroactively included them or not, but Z97 onwards was definitely a no.
 
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Re: Hypothetical Device to use NVMe storage to old PCs

Thu Jan 11, 2018 8:02 am

You'd need a carrier card with a PCIe bridge chip for using multiple M.2 cards within a single PCIe slot. I have found two such cards:

https://www.amazon.com/Aplicata-Quad-NV ... 1515673618

This first card only has an 8x PCIe 3.0 uplink so right off the bat with four M.2 drives, you'll only have half the peak possible bandwidth. If the host system only has PCIe 2.0 slots available, uplink bandwidth is again cut in half which corresponds to the link used by a single M.2 slot. Yep, a single fast M.2 drive could monopolize the entire uplink bandwidth.

https://www.thedebugstore.com/squid-pci ... -gen2.html

The second card has an 16x PCIe 2.0 uplink so bandwidth is cut in half as well and the links to the M.2 slots operate at PCIe 2.0 signaling speeds.

The other thing worth noting that these cards need host system support for them to be bootable. Hardware RAID support again would have to be provided by the host system but considering the bandwidth restrictions, (8x host uplink, PCIe 2.0 host uplink respectively), at most you'd get the performance of two M.2 drives. Software RAID would be lower performance. Overall RAID here is something I would not recommend.
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Re: Hypothetical Device to use NVMe storage to old PCs

Thu Jan 11, 2018 8:30 am

Just realized I misunderstood the OP when I wrote my first reply; I thought he was proposing two completely different things, one where the data goes over the PCIe bus and another where it's basically a NVMe to SATA adapter. I guess the idea was to use SATA only, to get around the BIOS boot support issue?

First of all, other than physical space, what would be the advantage of this over 2-4 regular SATA drives of smaller capacity?

Second, I'm not sure what you even mean by "fool older mobos into thinking its a 2-4 drive raid 0 array". The mobo sees 2-4 separate SATA connections, so all of the RAID logic needs to be on the mobo/OS side.

Third, since you're relying on the existing RAID support, there's no way to add TRIM support in the adapter. If the existing RAID doesn't understand TRIM, any information about which blocks need to be discarded has already been thrown away.

So what you're proposing is basically a fancy NVMe-to-SATA adapter with some logic to make the NVMe look like multiple logical drives (kind of a reverse port splitter). But it doesn't solve the TRIM issue for older RAID implementations (it can't!), and performance will be no better than a SATA-based RAID array.

You've saved a little space, reduced some cable clutter, and added a complicated custom chip (expensive!) to the data path. That's about it.
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