IBM storage billing for rented servers (like IBM Power Virtual Server / SAP workloads / IBM Cloud IaaS) is usually separate from compute, and it’s charged in a few structured ways rather than a single flat fee.

Here’s how it typically works:

💾 1. Main storage charging model (core idea)

IBM rental providers charge storage based on:

👉 ✔️ GB-hour (most common)

You pay for:

• How many GB you provision
• How long it is kept allocated (per hour)

So even if you don’t actively use the disk, it is still billed.

📌 Example:

• 500 GB storage attached for 1 month
  → billed as 500 GB × ~730 hours

📦 2. Storage types and how each is billed

🔹 A. Block / Data volumes (main disks for SAP)

• Charged per GB-hour
• Price depends on performance tier:

Typical tiers:

• Tier 0 (high performance SSD)
• Tier 1 (balanced)
• Tier 3 (cheaper / slower)

💡 Example behavior:

• You create a 100 GB disk → you pay for full 100 GB continuously
• Even if only 20 GB is used, billing is still for 100 GB

📌 Key point:

You are billed for provisioned size, not used space

🔹 B. Boot / image storage

• OS disk (AIX, Linux, SAP images)
• Also billed per GB-hour

But:

• Often included in VM cost bundle in some SAP offerings

🔹 C. Snapshot storage (backup copies)

• Charged separately per GB-hour
• Usually cheaper than active storage

Used for:

• backups
• recovery points
• system snapshots

🔹 D. Replication storage (DR systems)

If enabled:

• You pay for extra copied storage in another location
• Can almost double storage cost depending on setup

⚙️ 3. Performance tier affects cost heavily

Storage pricing changes based on:

📊 4. Simple real-world SAP example

Let’s say SAP system uses:

• 1 TB database volume
• 200 GB OS volume
• 300 GB backup snapshot

Monthly billing concept:

• 1500 GB total provisioned × hourly rate × 730 hours

👉 Even if database uses only 400 GB physically, you still pay for 1 TB provisioned.

💡 5. Important pricing rule (most important takeaway)

IBM storage is provisioned-based billing, not usage-based billing

So:

✔ You pay for allocated disk size
❌ Not actual data written
❌ Not compression savings inside OS

⚠️ 6. Common hidden cost drivers

• Over-provisioning (very common in SAP)
• Forgotten snapshots (keeps billing running)
• DR replication enabled unintentionally
• Large boot image backups
• High-performance tier selected by default

🧾 7. Quick summary

IBM rental storage costs are based on:

• 📦 GB provisioned
• ⏱️ time (hourly billing)
• ⚡ performance tier (IOPS level)
• 🔁 extra copies (snapshot / replication)