Not necessarily. One can capture 10G to disk using "only" a RAID-0 with 8-10 mechanical disks: it does the job both in bandwidth and space, and you can use regular filesystems such as XFS.
40G is a little bit more difficult: you need a huge RAID (simple, direct scaling: 32-40 disks) with mechanical disks to achieve the necessary bandwidth, and if you want to use SSDs you will need a lot of them too in order to have enough space to save any meaningful amount of traffic.
I remember seeing papers on on-the-fly compression for network traffic, but IIRC the results were not very impressive and the performance cost was noticeable.
40G is a little bit more difficult: you need a huge RAID (simple, direct scaling: 32-40 disks) with mechanical disks to achieve the necessary bandwidth, and if you want to use SSDs you will need a lot of them too in order to have enough space to save any meaningful amount of traffic.
I remember seeing papers on on-the-fly compression for network traffic, but IIRC the results were not very impressive and the performance cost was noticeable.