Exadata Storage Server (Cell Node)
Exadata Storage Servers, also called Cell Servers, are specialized storage nodes in Oracle Exadata.
Unlike traditional storage, Exadata storage performs database-aware processing such as Smart Scan, Storage Index filtering, and Flash Cache acceleration.
1. What is an Exadata Storage Server?
| Component | Description |
|---|---|
| Storage Server (Cell) | Physical server storing database data |
| Cell Server Software | Software running on storage nodes to manage I/O operations |
| Smart Scan | Offloads SQL processing to storage layer |
| Flash Cache | High-speed flash storage used for caching data |
2. Exadata Rack Storage Components
| Component | Typical Full Rack Count |
|---|---|
| Database Servers | 8 |
| Storage Servers | 14 |
| Network Switches | 2 |
3. Storage Server Processes
| Process | Purpose |
|---|---|
| CELLSRV | Main process handling I/O operations |
| MS (Management Server) | Monitors storage server health |
| RS (Restart Server) | Restarts failed services automatically |
4. Smart Scan Feature
Smart Scan allows Exadata to filter rows and columns directly on the storage servers.
Instead of sending full data blocks to the database server, only required rows are returned.
Traditional Storage: Database Server → Reads full blocks → Filters rows Exadata Smart Scan: Database Server → Storage Server filters rows → Sends only required data
5. Storage Index
Storage Index is an in-memory structure maintained by storage servers.
It helps avoid unnecessary disk reads by tracking minimum and maximum column values in storage regions.
6. Flash Cache
| Flash Usage | Description |
|---|---|
| Read Cache | Caches frequently accessed data blocks |
| Write Back Cache | Improves write performance |
| Smart Flash Cache | Automatically manages hot data |
7. Exadata Disk Architecture
Physical Disk
↓
LUN
↓
Cell Disk
↓
Grid Disk
↓
ASM Disk
↓
Database Files
8. Useful Storage Server Commands
cellcli -e list cell detail cellcli -e list celldisk cellcli -e list griddisk cellcli -e list flashcache
9. Advantages of Exadata Storage Servers
| Feature | Benefit |
|---|---|
| Smart Scan | Reduces data transfer and improves query performance |
| Storage Index | Avoids unnecessary disk reads |
| Flash Cache | High-speed data access |
| RDMA Network | Ultra-low latency communication |
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