2 ms·
Well, attaching 10 PCIe devices is going to give a very hard time to your CPU if all of them should be used. The speed of copying from memory or between device
by crabbone 4y ago
Well, attaching 10 PCIe devices is going to give a very hard time to your CPU if all of them should be used. The speed of copying from memory or between devices will become a bottleneck. Another problem is that on such a machine you will also need huge amount of memory to allow for copying to work. And, if you want this to work well, you'd need some high-end hardware to be actually able to pull that off. In such a system, your CPU will prevent you from exploiting the possible benefits of parallelization. It seems beefy, but it's entirely possible that a distributed solution you could build with a fraction of the cost would perform just as well.
This situation may not be reflected in Azure pricing (the calculator gives 7.68 $/h for L80as_v3) since if MS has such hardware, it would be a waste for it to stand idle. They'd be incentivized to rent it out event at a discount (their main profit is from traffic anyways). So, you may not be getting an adequate reading of the situation, if you are trying to judge it by the price (rather than cost). But, this is only the price of the VM, I'm scared to think about how much you'd pay if you actually utilize it to its full potential.
Also, since it claims to have 80 vCPUs, well... it's either a very expensive server, or it's, again, a distributed system, where you simply don't see the distributed part. I haven't dealt with such hardware firsthand, but we have in our DC a Gigaio PCIe TOR switch which would allow you to have that much memory (in principle, we don't use it like that) in a single VM. That thing with the rest of the hardware setup costs some six-digit number of dollars. I imagine something similar must exist for CPU sharing / aggregation.