EBS snapshots that belong in the archive tier
What does ZopNight detect here?
EBS snapshot archive costs $0.0125 per GB-month against $0.05 for standard, a 75% reduction. ZopNight flags snapshots older than 90 days and larger than 50 GB, where the saving is worth the tradeoff: restoring from archive takes 24 to 72 hours.
Signal and threshold
| Field | Value |
|---|---|
| Rule IDs | RC-1513 |
| Category | rightsizing |
| Severity | low |
| Metric | none — pure configuration read |
| Source | ebs_snapshot_tier.go |
Where it applies
The arithmetic
| Tier | Rate | 500 GB snapshot |
|---|---|---|
| Standard | $0.05 / GB-month | $25.00 / month |
| Archive | $0.0125 / GB-month | $6.25 / month |
A flat 75% saving against the published snapshot storage rates, and the only cost is restore latency.
Why the two thresholds
Older than 90 days. A recent snapshot is plausibly part of an active restore path. One that has sat untouched for a quarter is being kept for retention or compliance, and retention copies do not need to be instantly restorable.
Larger than 50 GB. Archiving has a per-snapshot overhead, and below roughly this size the absolute saving is not worth the restore penalty on something you might actually need.
The tradeoff you are accepting
Restoring an archived snapshot takes 24 to 72 hours. That is not a slow download, it is a tier transition you cannot rush.
Which makes the real question: is this snapshot part of a recovery plan with an RTO? If your disaster-recovery runbook says “restore from snapshot”, archiving it silently breaks that runbook, and you find out during the incident. Archive retention copies, never recovery copies.
Listing snapshots by size and StartTime
aws ec2 describe-snapshots --owner-ids self --query 'Snapshots[?VolumeSize>`50`].[SnapshotId,VolumeSize,StartTime,Description]' --output tableSort by StartTime and look at anything past 90 days.
Fixing it
Archive through the EC2 console or aws ec2 modify-snapshot-tier. The change is reversible
(restoring moves it back to standard), but each transition takes time, so it is not something to
toggle repeatedly.