How Viable is PCIe 2.0 Today?

[darkarn]

Simple question: is having only PCIe 2.0 good enough, (be it for a simple home server all the way to enterprise setups)? Or should I start selling off such gear (namely CPU and mobo) and aim for PCIe 3.0 stuff?

 

[Terry Kennedy]

Simple question: is having only PCIe 2.0 good enough, (be it for a simple home server all the way to enterprise setups)? Or should I start selling off such gear (namely CPU and mobo) and aim for PCIe 3.0 stuff?

It depends on what you're doing and the hardware involved. An Intel X540-T2 dual 10GbE card isn't bandwidth-limited in a PCIe 2 x8 slot, and any reasonable number of spinning hard drives shouldn't be, either. If you're doing 40GbE or plan on building storage out of SSDs, then that changes things. As far as selling off and buying new(er) parts, you need to see if the expansion cards you have support PCIe 3 as well - otherwise you're just moving the bottleneck from the mainboard to the expansion cards.

 

[EffrafaxOfWug]

Depends entirely on your bandwidth requirements as to whether it's "good enough", but it's an unlikely PCIe 2.0 device that is faster than the bus it's designed to be plugged in to. If it ain't not fixed, don't not unbreak it.

 

[BLinux]

It depends on what you're doing and the hardware involved. An Intel X540-T2 dual 10GbE card isn't bandwidth-limited in a PCIe 2 x8 slot, and any reasonable number of spinning hard drives shouldn't be, either. If you're doing 40GbE or plan on building storage out of SSDs, then that changes things. As far as selling off and buying new(er) parts, you need to see if the expansion cards you have support PCIe 3 as well - otherwise you're just moving the bottleneck from the mainboard to the expansion cards.

+1 on all the above points. I think @Terry Kennedy took all the words out of my mouth.

 

[darkarn]

It depends on what you're doing and the hardware involved. An Intel X540-T2 dual 10GbE card isn't bandwidth-limited in a PCIe 2 x8 slot, and any reasonable number of spinning hard drives shouldn't be, either. If you're doing 40GbE or plan on building storage out of SSDs, then that changes things. As far as selling off and buying new(er) parts, you need to see if the expansion cards you have support PCIe 3 as well - otherwise you're just moving the bottleneck from the mainboard to the expansion cards.

+1 on all the above points. I think @Terry Kennedy took all the words out of my mouth.

Thanks guys! I understand that if I somehow decide to upgrade to newer 10GbE cards (e.g. ConnectX-2 to ConnectX-3), they are on PCIe 3.0 too but it sounds like for 10Gbe, unless the cards are using only 4 PCIe lanes instead of 8, being on PCIe 2.0 won't be a problem just like the Intel card right?

Depends entirely on your bandwidth requirements as to whether it's "good enough", but it's an unlikely PCIe 2.0 device that is faster than the bus it's designed to be plugged in to. If it ain't not fixed, don't not unbreak it.

Thanks, good advice indeed. I just want to see if I should let go now or just keep using them until they really break down

 

[EffrafaxOfWug]

Thanks guys! I understand that if I somehow decide to upgrade to newer 10GbE cards (e.g. ConnectX-2 to ConnectX-3), they are on PCIe 3.0 too but it sounds like for 10Gbe, unless the cards are using only 4 PCIe lanes instead of 8, being on PCIe 2.0 won't be a problem just like the Intel card right?

Mostly correct but depends on the type of card. Using a specific example of the ConnextX3 single-port 10GbE cards, one of those can use a maximum of (2*10)/8 = 2.5GB/s, or 1.25GB/s in each direction, so even if it comes in a 3.0 4x interface (just under 4GB/s each direction), it wouldn't be potentially bottlenecked on a 2.0 4x interface (~2GB/s each direction), even under a fully duplexed load (of the sort I'd never have at home).

If you're buying new kit you can just get the PCIe 3.0 stuff to use with your existing hardware, and then upgrade if and when PCIe 2.0 on your motherboard becomes a bottleneck, but I don't think it makes economic sense to do so until you hit real-world performance limitations.

There's a handy table here showing more accurate differences across the various generations and the amount of bandwidth you can expect to get of of various slots.

I just want to see if I should let go now or just keep using them until they really break down

It's the frugal Scot in me talking as I just tend to use things until they break down or become completely obsolete or incompatible anyway, but I'm pretty hardware-light as far as most people on this forum are concerned and the s/h market in the EU isn't anything like the US. If you think there's an economic case to be made for unloading your older kit now then do so, but if you don't your wallet (and the environment!) might thank you.

 

[darkarn]

Mostly correct but depends on the type of card. Using a specific example of the ConnextX3 single-port 10GbE cards, one of those can use a maximum of (2*10)/8 = 2.5GB/s, or 1.25GB/s in each direction, so even if it comes in a 3.0 4x interface (just under 4GB/s each direction), it wouldn't be potentially bottlenecked on a 2.0 4x interface (~2GB/s each direction), even under a fully duplexed load (of the sort I'd never have at home).

If you're buying new kit you can just get the PCIe 3.0 stuff to use with your existing hardware, and then upgrade if and when PCIe 2.0 on your motherboard becomes a bottleneck, but I don't think it makes economic sense to do so until you hit real-world performance limitations.

There's a handy table here showing more accurate differences across the various generations and the amount of bandwidth you can expect to get of of various slots.

It's the frugal Scot in me talking as I just tend to use things until they break down or become completely obsolete or incompatible anyway, but I'm pretty hardware-light as far as most people on this forum are concerned and the s/h market in the EU isn't anything like the US. If you think there's an economic case to be made for unloading your older kit now then do so, but if you don't your wallet (and the environment!) might thank you.

I have the ConnectX-2 cards already but was just calculating if shifting to ConnectX-3 (and PCIe 3.0) would be worth my while. I don't see how a HDD (or a SSD even!) can saturate the 2GB/s limit so it looks like upgrading these cards just for the supposedly speed increase do not seem worthwhile. (Firmware issues notwithstanding but I think the other thread is more suited to answer that)

And thanks for giving me that perspective; I am from Singapore where hardware do not come cheap either! I am just unsure if PCIe 2.0 is considered obsolete in today's standards which is why I made this thread to get some ideas about it.

 

[Waterkippie]

It's not obsolete at all, PCIe 2.0 is 500MB/s per lane, so even a x2 slot would be enough for a single port 10G card.

x4 for a dual port 10g card
x8 for a single port 40g card