Object Storage vs Block Storage for database backups: performance and cost trade-offs

Cloud Platforms Oracle Cloud
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1

We’re designing our backup architecture for multiple Oracle databases in OCI and debating between Object Storage and Block Storage for RMAN backups. Currently using Block Volumes mounted to DB servers, but Object Storage seems more cost-effective for long-term retention.

Our environment: 8 databases ranging from 500GB to 5TB, daily incrementals, weekly fulls, 90-day retention. Block Storage gives us faster backup/restore speeds (around 400MB/s), but costs are adding up. Object Storage is cheaper but I’m concerned about restore times during emergencies.

Has anyone done detailed performance and cost analysis between these approaches? What’s the real-world impact on recovery time objectives when using Object Storage with RMAN? Are there hybrid strategies that balance both concerns?

2

Consider your actual RTO requirements carefully. If you need sub-2-hour recovery, Block Storage is safer. But most organizations overestimate their RTO needs. We surveyed our business units and found only 2 of 15 databases truly needed rapid recovery. The rest could tolerate 4-6 hour RTOs, making Object Storage perfectly viable. Also factor in that Object Storage provides built-in replication across availability domains, reducing your disaster recovery complexity.

3

We made this exact transition last year. Object Storage backup speeds are slower (100-150MB/s typically) but for most scenarios, it’s acceptable. The cost savings are massive - we cut backup storage costs by 65% moving from Block to Object Storage for backups older than 7 days. Keep recent backups on Block Storage for fast recovery, archive older ones to Object Storage.

4

You can automate the lifecycle using Object Storage lifecycle policies combined with RMAN’s backup retention policy. Configure RMAN to write directly to Object Storage using sbt_tape, then use Object Storage lifecycle rules to move backups older than 30 days to Archive tier automatically. This gives you fast recent restores while minimizing long-term costs. We’ve scripted this with OCI CLI to monitor backup age and trigger transitions.

5

Let me synthesize the discussion with detailed analysis across all three focus areas:

Object Storage Integration with RMAN:

Object Storage integration requires configuration but provides excellent reliability once established. Key implementation points:

  1. Setup Method: Use OCI’s sbt_tape library (libopc.so) which integrates RMAN with Object Storage as a virtual tape device. Configuration is straightforward with proper credential setup.

  2. Performance Characteristics:

    • Backup throughput: 100-180MB/s depending on network and RMAN channel configuration
    • Restore throughput: 120-200MB/s (slightly better than backup due to read optimization)
    • Latency: 20-50ms for first byte, then streaming throughput
    • Parallelism: Scales well with multiple RMAN channels (we use 4-8 channels)

  3. Reliability: Object Storage provides 99.9% durability with automatic replication. No risk of disk failure like Block Volumes. Built-in versioning protects against accidental deletion.

  4. Integration Benefits: Direct RMAN integration means no manual file management. Backups are automatically tracked in RMAN catalog with Object Storage as the storage tier.

Block Storage Performance Analysis:

Block Storage advantages:

  1. Raw Performance: 400-500MB/s throughput with Ultra High Performance volumes, 3-5ms latency
  2. Simplicity: Standard filesystem operations, no special configuration needed
  3. Fast Recovery: Critical for tier-1 databases with aggressive RTO requirements (under 2 hours)
  4. Flexibility: Easy to mount/unmount, resize, or snapshot

Block Storage disadvantages:

  1. Cost: 67% more expensive than Object Storage Standard tier
  2. Manual DR: Requires cross-region volume replication setup for disaster recovery
  3. Capacity Planning: Must pre-provision capacity, can’t grow indefinitely like Object Storage
  4. Management Overhead: Need to monitor disk usage, manage old backups manually

Backup Cost Analysis - Real Numbers:

For your environment (8 databases, 90-day retention):

Scenario 1: All Block Storage

  • Estimated backup storage: ~45TB (with incrementals and fulls)
  • Monthly cost: 45,000 GB × $0.0425 = $1,912.50
  • Annual cost: $22,950

Scenario 2: All Object Storage (Standard tier)

  • Same 45TB storage
  • Monthly cost: 45,000 GB × $0.0255 = $1,147.50
  • Annual cost: $13,770
  • Savings: $9,180/year (40% reduction)

Scenario 3: Hybrid Tiered Approach (RECOMMENDED)

  • Recent backups (14 days) on Block Storage: ~8TB
  • Older backups (76 days) on Object Storage Standard: ~32TB
  • Archived backups (moved to Archive tier after 60 days): ~15TB

Monthly costs:

  • Block Storage: 8,000 GB × $0.0425 = $340
  • Object Storage Standard: 32,000 GB × $0.0255 = $816
  • Object Storage Archive: 15,000 GB × $0.0010 = $15
  • Total monthly: $1,171
  • Annual cost: $14,052
  • Savings vs all Block: $8,898/year (39% reduction)
  • Performance benefit: Fast 14-day recovery window

Recommended Hybrid Strategy:

  1. Tier 1 Databases (critical, RTO < 2 hours):

    • Last 7 days on Block Storage
    • Days 8-90 on Object Storage Standard
    • Use RMAN to backup directly to Block, then script to move to Object Storage

  2. Tier 2 Databases (standard, RTO 4-8 hours):

    • Last 3 days on Block Storage
    • Days 4-60 on Object Storage Standard
    • Days 61-90 on Object Storage Archive tier

  3. Tier 3 Databases (non-critical, RTO > 8 hours):

    • All backups directly to Object Storage Standard
    • Move to Archive tier after 30 days

Implementation Automation:

Create lifecycle automation using OCI CLI scripts:

  • Monitor RMAN backup completion
  • Identify backups older than threshold (7/14 days)
  • Copy from Block Storage to Object Storage
  • Verify integrity and delete from Block Storage
  • Apply Object Storage lifecycle policies for Archive tier transition

The sweet spot for most organizations is the hybrid approach - maintaining fast recovery capability for recent backups while leveraging Object Storage’s cost efficiency for long-term retention. This balances your RTO requirements with budget constraints, typically reducing backup storage costs by 35-45% while keeping critical recovery operations fast.

6

One factor people overlook: Object Storage integration with RMAN requires the Oracle Cloud Infrastructure Object Storage Tool or sbt_tape library configuration. This adds complexity but works reliably once set up. Block Storage is simpler - just mount and backup to disk. For critical production databases where RTO is under 4 hours, I’d keep Block Storage. For less critical systems, Object Storage makes financial sense. We use a tiered approach based on database criticality.