The Egress Trap: Modeling Cloud Cold Tiers Honestly Against Tape

The Egress Trap: Modeling Cloud Cold Tiers Honestly Against Tape

By The LTO Show Editorial Staff

The pitch is seductive: archive your cold data to S3 Glacier Deep Archive for less than $1 per terabyte per month. At that surface rate, cloud cold storage appears to decisively undercut a purpose-built LTO tape system. But that number is doing most of its work in the dark — and when you actually model the full economics, the comparison shifts dramatically.

The Advertised Rate vs. The Real Bill

AWS S3 Glacier Deep Archive lists storage at $0.00099/GB/month (~$0.99/TB/month). Microsoft Azure Archive Blob Storage runs at the same figure in US East. Google Cloud Archive Storage sits at $0.0012/GB/month. All cheap on their face.

The trap is egress. AWS charges $0.09/GB to move data out of its network (after 100 GB/month free). Glacier retrieval stacks a separate fee on top: $0.0025/GB for Bulk (12-hour restore window) or $0.02/GB for Standard (3–5 hours). Restore one petabyte on a Bulk retrieval and you’re looking at $2,500 in retrieval fees plus roughly $90,000 in egress transfer costs. A $1,014/month storage line item becomes a $93,000+ one-time event the moment a major restore lands.

Running the Numbers at Petabyte Scale

LTO-9 delivers 18 TB native per cartridge at approximately $20/cartridge — around $1.11/TB on media alone. A mid-range 48-slot LTO-9 tape library with two drives runs roughly $50,000–$80,000 capital. Amortized over seven years (standard drive longevity) and loaded to 10 PB, the all-in cost including media, power, and maintenance typically lands between $0.003–$0.006/GB/year — with zero egress cost, ever.

At that scale, a single full cloud restore can exceed the entire multi-year capital cost of an equivalent tape infrastructure.

What the TCO Model Must Include

Honest total-cost-of-ownership analysis requires more than the storage-rate headline:

  • Retrieval frequency — Even one full restore per year fundamentally undermines cloud cold economics at petabyte scale.
  • Retention horizon — Per-TB/month cloud fees compound continuously; tape media depreciation flattens sharply after year one.
  • Minimum storage durations — Glacier Deep Archive enforces a 180-day minimum per object. Early deletes still bill.
  • Access latency — Bulk Glacier retrieval takes 12 hours. A well-configured LTO library can deliver first-byte access in minutes.

Egress Is Not a Footnote

Cloud cold tiers are a defensible fit for small volumes with no realistic restore exposure. For petabyte-class archives — media production vaults, research repositories, government records, post-production MAMs — the egress math dismantles the headline storage rate entirely. Tape doesn’t hide its costs. Cloud cold tiers often do, until the restore invoice arrives.

More on this across Industry Insights. Contact us at info@ltoshow.com.

Citations

Questions or comments? We’d love to hear from you — reach the editorial team at info@ltoshow.com.

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