Future of USB vs SATA3, M.2/NVME

[bobad]

Been wondering, since USB is getting faster and faster, can it, will it ever replace SATA and NVME? Does anyone know if there is anything inherent in USB that makes it unlikely to become the boot drive as well as accessory drive controller? USB-C flavors can theoretically transfer up to 40gbps, so will this speed ever be tapped for the regular boot drive?

Maybe some day computers will have a single type of controller for data, video, accessories, and even CPU. (Yes I know NVME drives run through the video bus)

Thoughts?

 

[trents]

A couple of months ago there was a thread on this forum that got into that question somewhat. The thread actually centered around the confusing nomenclature of all the USB standards that have come down the pike over the years and was spawned by a recent announcement that yet another one was on the horizon that promised (if I recall correctly) transfer rates that were getting fast enough to make one wonder if USB bandwidth adequate for gaming level video signal transmission was next up.

 

[Dolk]

To answer your question directly bobad, no USB would never replace direct attach NVMe. USB may get to faster speeds, but its always over the protocol of USB. NVMe is a direct attach via PCIe which is a much more broader and native format for modern x86 CPUs. You may see more micros or lower end processors take advantage of USB for that purpose, but PCIe will always win over USB in support and utilization when it comes to storage.

 

[HankB]

USB - Universal Serial Bus. Implicit in it's name is that it is intended to attach anything convenient to a PC including keyboard/mouse, Network adapters, mass storage including flash devices and hard drives, CDROMs and so on. As a general rule, things designed to do everything often have to sacrifice performance or capabilities for any specific task. In the case of USB that involves extra protocol overhead to manage the wide array of devices. While that doesn't matter much when it comes to mouse/keyboard, it will have an impact for mass storage devices. One additional issue with USB (that I have been told) is that a mass storage device is allowed to tell the host that a write has completed even though it has not. This can be risky for disk file systems should the device not then be able to complete that operation.

ATA, SATA and NVME were designed from the ground up to support mass storage devices. That's the only thing they do so they can be highly tuned for that specific purpose.

One new thing that looks like USB but is not is Thunderbolt. This extends PCI lanes directly in a USB-C connector and which allows high speed devices such as mass storage and graphics adapters to operate at full speed. The connectors can be backwards compatible with USB-C but they have capabilities that are not covered by the USB standard.

 

[JrClocker]

USB has an overhead in it for all data transactions...I think about 10% or so. Add to this that USB also has a time-lag for data transfer similar to Ethernet (the data is transmitted in packet form, and an entire packet needs to be received, error detected, etc.)

So, at current speeds, SATA is superior to USB 3 (non-C) for bulk media transfers.

USB 3.1-C is much faster than current SATA connections (10 Gbps vs 6 Gbps). This more than compensates for the USB overhead...but still does not fully compensate for the data time-lag.

If SATA speed is not increased, then in the near future USB will overtake SATA for bulk storage.

 

[EarthDog]

USB 3.1-C is much faster than current SATA connections (10 Gbps vs 6 Gbps).

Note there are 2 USB 3.1 protocols... Gen1 and Gen2. Gen 1 = 5 Gbps while Gen 2 = 10 Gbps. Just because the connector is Type-C doesn't mean its 3.1 G2/10 Gbps. There are plenty of boards out there for example which have Type-C G1/5 Gbps connections.

 

[Dolk]

JrClocker, SATA will not be going away for some time. Most consumer grade systems will continue to use SATA until direct attach NVMe drives come down in price and connector prices are comparable. Most likely what will happen is Gen4/5 PCIe will bridge out to multiple x2/x4 Gen3/4 PCIe connectors to incorporate massive storage. You already see this with the U.2 connectors on the Xeon and Threadripper workstation/high end motherboards. But they use a Gen3 x8/16 port and use a bridge chip to control the flow of the PCIe to the CPU.

 

[EarthDog]

I agree... SATA will be here for a while. Prices on M.2 modules, both SATA and NVMe have been coming down in price, but a more standard 2.5"/7mm SATA drives still hold the capacity /$ crown.

That said, we already have boards with multiple M.2 slots on it with full or limited bandwidth (depends on the platform/PCIe lanes, etc). To be quite honest, I think space on a board is a big issue... where do you put 6 M.2 slots? I suppose a row of M.2 slots and cable connected to M.2 drives mounted on cases can be a solution? I don't know... but I think space and of course bandwidth are big obstacles to overcome.

 

[Dolk]

Yeah I forgot to also mention the cost of cables. PCIe cables are still relatively more expensive than SATA cables. So you have a point ED that M.2 slots are more welcoming in terms of price comparison of a NVMe direct attach drive that fits into a 2.5 bay. However, you are already seeing what could happen. We have DIMM2 slots that are made for M.2 risers. There is also the relatively lower cost U.2 but it requires an expensive backplane to handle the PCIe routing between all the NVMe / SATA drives.

I think short term will always be use spare PCIe for as many M.2 as possible, and than let the Southbridge handle all the SATA connections it can. Wait for PCIe 4/5 to mature and see where the market goes. Storage is getting better to where consumers don't need as many number of drives, but there will always be a market for those that want to. The high number of SATA ports these days is just due to the fact all of it is cost free at a manufacturing level.

 

[EarthDog]

U.2 can just leave consumer boards all together as far as I am concerned. Maybe only on HEDT or workstation class boards... otherwise, stay in the DC where they belong.

 

[petteyg359]

Note there are 2 USB 3.1 protocols... Gen1 and Gen2. Gen 1 = 5 Gbps while Gen 2 = 10 Gbps. Just because the connector is Type-C doesn't mean its 3.1 G2/10 Gbps. There are plenty of boards out there for example which have Type-C G1/5 Gbps connections.

Originally known as USB 3.0 and USB 3.1, until the marketing departments shat all over everything. And a Type-C connector doesn't have anything to do with USB 3.x but that they came to market near each other. Type C is just a physical specification that can go on any bus, even 2.0.

USB has an overhead in it for all data transactions...I think about 10% or so. Add to this that USB also has a time-lag for data transfer similar to Ethernet (the data is transmitted in packet form, and an entire packet needs to be received, error detected, etc.)

So, at current speeds, SATA is superior to USB 3 (non-C) for bulk media transfers.

That's what UASP is for. USB 3.0 overtook SATA for storage (at least removable or hot-swap, maybe not permanent internal) as soon as chipsets started supporting UASP, which was years ago. Much increased speed and vastly reduced CPU usage on par with a normal SATA drive.

 

[EarthDog]

Originally known as USB 3.0 and USB 3.1, until the marketing departments shat all over everything. And a Type-C connector doesn't have anything to do with USB 3.x but that they came to market near each other. That's a physical specification and has nothing to do with speed. You can put a Type-C connector on a USB 2.0 bus.

As I said too... spot on! They Type-C connector doesn't tell you how fast the connection is.