Disk and tape are different jobs
The split is not about cost alone. Disk (eos) serves what is being analysed right now: random access, high concurrency, thousands of jobs reading at once. Tape (cta) holds the custodial copy: sequential, cheap per byte, and — the part that matters — offline by default, which makes it resistant to the failure modes that take out online systems. Getting the boundary right is what keeps the archive affordable and the analysis fast.
Topology
- Part of: storage-and-data
- About: eos
- About: cta
- Cites: eos-run3-storage — the division of labour between the two layers.