Re: So what's happening to the Isambard 2 hardware?
The reality is that it is too old to be of any use for it's intended purpose and much of the hardware too specialised to be repurposed. Most will simply be recycled.
HPC facilities generally have a higher hardware churn anyway as by there very nature they tend to have workloads that are already pushing normal compute boundaries. If you cluster is using 1MW and after 2 years you can double the performance, memory or storage for the same power draw then as long as the money is available it will be replaced or upgraded.
We rotated the hardware round:
Tier 1 -> business justification to run the jobs.
Tier 2 -> general availability as it was the hardware from the previous cluster.
Both ran at about 98% utilisation most of the time. That is called "sweating your assets". Boy were the hot aisles hot!
When they were replaced it was generally on a very modest "buy-back" where some parts would be reused and the rest recycled.