Optical media, ranked by cost per terabyte

Recordable optical media — Blu-ray (BD-R), DVD±R and CD-R — stores data as physical marks burned into a disc, creating a true write-once archive that can’t be altered by malware, accidental deletion or a controller failure. That immutability is optical’s enduring appeal: a burned disc is an offline, air-gapped copy that survives ransomware and bit-rot in ways a connected drive cannot. For capacity it can’t compete with hard drives, but recordable Blu-ray reaches usable sizes — 25 GB single-layer, 50 GB dual-layer, and 100 GB BDXL triple-layer — that make small, durable archives practical.

On cost per terabyte, Blu-ray is far and away the best optical value — DVDs and especially CDs hold so little that their $/TB is very high despite cheap discs. The format earns its place not on price but on properties: low-cost archival-grade ‘M-DISC’ Blu-ray is rated to last centuries, discs need no power, and they’re trivially stored off-site. The trade-offs are slow write speeds, the need for a burner drive, and capacities measured in tens of gigabytes per disc. When comparing value, focus on Blu-ray for any meaningful archive, note single vs dual vs triple layer, watch pack quantity, and prefer reputable media brands for long-term reliability.

Blu-ray vs DVD vs CD for archival

All three store data optically, but capacity differs by orders of magnitude, and that gap dominates cost per terabyte. For archiving anything beyond a handful of documents, Blu-ray is the only optical format that makes sense on value.

For genuinely permanent storage, look for archival-grade discs (often branded M-DISC) that resist humidity and light far better than standard dye media. Optical is one leg of a wider plan — combine it with disk and off-site copies as in our backup strategy guide.