40 Gigabits per second is roughly 4 Gigabytes per second.

4 Gigabytes per second times 86400 seconds per day is 345,600 Gigabytes per day.

Roughly: 345 Terabytes per day.

Large, but not stupidly so.

40 Gbps would actually be exactly 5 Gigabytes per second (divided by 8).

While I don't know the exact overhead of 10GigE, there is likely still some overhead.

At the lower speeds, things like 8b/10b encoding and Reed-Solomon ECC added enough overhead that dividing by 10 was more accurate than dividing by 8.

> While I don't know the exact overhead of 10GigE, there is likely still some overhead.

on 10gige pipes, at max Ethernet mtu (1500) bytes etc, there is approx. 94% of available bandwidth for user data (accounting for things like inter-frame-gap, crc checksums etc). with jumbo-frames that number goes to 99%.

Okay, so call it 10% overhead (actually 8%) if we're taking a WAG (wild *ss guess).

That would mean that I would need to divide by about roughly nine (8.8 or so).

Sorry, I can't do divide-by-nine quickly in my head. I can do divide by 10 though, and my error is roughly 10%.

> 40 Gigabits per second is roughly 4 Gigabytes per second.

it should be 5GB/s right ? :)

> where you dump packet stream from 4x10gbps cards with minimal 84b size (on ethernet), show that you would exhaust the storage in approx. 4.5 minutes

I don't understand your relations here, or the size of the storage you're considering. I did this:

3.5 million packets per second * 84 bytes per packet * 4 interfaces == 101.606 terabytes/day.

Or, at the raw interface rate:

10 Gb/s * 4 interfaces == 432 terabytes/day.

> or the size of the storage

whoopsie, i was considering 1.2tb of storage...

> 3.5 million packets per second

it is actually, 14.88 Mpps.