very fast NAS 4GBe or DAS USB3
- Thread starter frank10
- Start date
Well I had a quick read on the theoretical vs. actual speeds since I don't exactly remember how it was with USB2 and never looked into USB3 that much.
For USB2 it was half duplex meaning the same channels where used for traffic to both ways. When return messages are coming back it can't send anything at the same time. Theoretical max speeds were 480mbit/s (or 60MB/s), in practise you would get about half of that.
USB3 is full duplex with a max theoretical speed of 5gbit/s (or 640MB/s), in practise it seems to top out around 150-200MB/s. Based on a quick read it seems the problem is that the transmitted data needs to be encoded and decoded on the other end to reduce errors, this reduces throughput by about 10-20% (theory is similar to TCP overhead, you end up at around 400MB/s after taking both encoding, decoding and flow control into consideration). Most performance lost after the theoretical 400MB/s seems to be up to the controllers on the device and end computer and drivers. This actually explains why I can get less then 100MB/s from a 1TB Sandisk Extreme Pro with the USB3 connector that I got with my Samsung Evo 840, but others have gone over 200MB/s with good USB3 enclosures... I guess the enclosure handles a lot of the encoding / decoding and reaching even close to the theoretical maximum would require some expensive hardware that is just not available for consumers.
Maybe USB 3.1 will change this? Then you get to Thunderbolt which always performs better... Apart from having higher theoretical maximum speeds and a different design, they also have a lot tighter control over what is allowed to be sold under the brand. I guess you end up with less junk, but also less devices in general do to the manufacturers expense in validating new designs.
For USB2 it was half duplex meaning the same channels where used for traffic to both ways. When return messages are coming back it can't send anything at the same time. Theoretical max speeds were 480mbit/s (or 60MB/s), in practise you would get about half of that.
USB3 is full duplex with a max theoretical speed of 5gbit/s (or 640MB/s), in practise it seems to top out around 150-200MB/s. Based on a quick read it seems the problem is that the transmitted data needs to be encoded and decoded on the other end to reduce errors, this reduces throughput by about 10-20% (theory is similar to TCP overhead, you end up at around 400MB/s after taking both encoding, decoding and flow control into consideration). Most performance lost after the theoretical 400MB/s seems to be up to the controllers on the device and end computer and drivers. This actually explains why I can get less then 100MB/s from a 1TB Sandisk Extreme Pro with the USB3 connector that I got with my Samsung Evo 840, but others have gone over 200MB/s with good USB3 enclosures... I guess the enclosure handles a lot of the encoding / decoding and reaching even close to the theoretical maximum would require some expensive hardware that is just not available for consumers.
Maybe USB 3.1 will change this? Then you get to Thunderbolt which always performs better... Apart from having higher theoretical maximum speeds and a different design, they also have a lot tighter control over what is allowed to be sold under the brand. I guess you end up with less junk, but also less devices in general do to the manufacturers expense in validating new designs.
What's that route? I still often use the disks I have with FW800, at least with more pleasure then USB2
I guess Thunderbolt has more chance to be popular as Intel is closely involved, but it might also be a bit like SCSI, which had very good advantages over IDE, but still was not something most people would have been ready to pay for since they just don't need it.
I think TB will remain longer than FW.
At least the FW bandwidth could be equal to other solutions, while TB bandwidth can't be surpassed by ANYthing today, we are talking of 20Gbs!
The best you can rival is 5Gbs of USB3 but with all the limitations we saw.
Also the next steps will be 40Gbs TB3 vs 10Gbs USB4.
The point is: there's nothing comparable to a TB connection! Only when it will be, we could think of its disappearing.
The only real shame is the lack diffusion on pc side, but I hope it will change soon.
At least the FW bandwidth could be equal to other solutions, while TB bandwidth can't be surpassed by ANYthing today, we are talking of 20Gbs!
The best you can rival is 5Gbs of USB3 but with all the limitations we saw.
Also the next steps will be 40Gbs TB3 vs 10Gbs USB4.
The point is: there's nothing comparable to a TB connection! Only when it will be, we could think of its disappearing.
The only real shame is the lack diffusion on pc side, but I hope it will change soon.
I don't think there was any reason why Firewire could not become an industry standard. It was very standard on macs, but on PC's only included in high end motherboards for workstations... I think the main use cases would have been faster external storage and better sound cards, both of which were quite niche markets so bulk motherboard manufacturers did not see a business case in including it more commonly.
In that sense TB is a similar case even though it might have a bit better backing. It will never get included in the bulk motherboards, and the use cases where it's even required are somewhat limited to specialist areas needing higher throughput then USB can deliver. When USB 3.1 becomes more common this case will be even stronger.
However there was never anything wrong with Firewire, it works very well and while it's starting to vanish I'd just say time has passed it. If thunderbolt connections are backward compatible it might give it a longer usable time which could make it more standard... Anyway, in this case it seems the only good options for fast DAS connections are TB, 10G ethernet or fiber which are all kind of niche products (10G ethernet being the option that will be viable for the longest time).
In that sense TB is a similar case even though it might have a bit better backing. It will never get included in the bulk motherboards, and the use cases where it's even required are somewhat limited to specialist areas needing higher throughput then USB can deliver. When USB 3.1 becomes more common this case will be even stronger.
However there was never anything wrong with Firewire, it works very well and while it's starting to vanish I'd just say time has passed it. If thunderbolt connections are backward compatible it might give it a longer usable time which could make it more standard... Anyway, in this case it seems the only good options for fast DAS connections are TB, 10G ethernet or fiber which are all kind of niche products (10G ethernet being the option that will be viable for the longest time).
That's the history of FireWire too!
sfx2000
Part of the Furniture
FW was perhaps too good - as a result, it was really adopted at the higher end of the peripheral market, whereas USB2.0 was "good enough"...
Same thing is happening with TB/TB2 - expansion is expensive, but the utility again, it appeals really towards the higher end "pro" market... There's a lot of Mac's out there with Thunderbolt ports, and most of them aren't used - and if they are, it's normally as a monitor adapter using the Mini-Display port functionality.
That being said - right now, it's hands down the fastest external interface you can get in Consumer/Pro space, it's basically a PCI-e slot externalized... it's faster than eSATA, faster than USB3.0, and is more flexible - but all of this comes as a substantially higher cost because again, the peripherals are targeted towards the high end, where USB3 is, again, good enough for most folks..
Same thing is happening with TB/TB2 - expansion is expensive, but the utility again, it appeals really towards the higher end "pro" market... There's a lot of Mac's out there with Thunderbolt ports, and most of them aren't used - and if they are, it's normally as a monitor adapter using the Mini-Display port functionality.
That being said - right now, it's hands down the fastest external interface you can get in Consumer/Pro space, it's basically a PCI-e slot externalized... it's faster than eSATA, faster than USB3.0, and is more flexible - but all of this comes as a substantially higher cost because again, the peripherals are targeted towards the high end, where USB3 is, again, good enough for most folks..
USB is just dirt cheap and enough. Selecting TB on the pc side into a laptop is at the same time selecting a lot of other things and might multiply the price of your computer. This is up to the manufacturers more then anything...
How big a percentage of PC laptops are still sold without a SSD? With a cheap display? With less then 8 hours battery life? Probably 95% because even looking at my own relatives they just go and pick some cheap piece of junk, and with low margins it's exactly what they get.
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