Let’s compare Exadata Database Service on Exascale Infrastructure (ExaDB-XS) and Exadata Database Service on Dedicated Infrastructure (ExaDB-D) and review how to choose between these services. Both Oracle Database services run on powerful Exadata hardware within the Oracle Cloud Infrastructure (OCI) public cloud, but they differ in their underlying infrastructure model and characteristics.

• Exadata Database Service on Dedicated Infrastructure (ExaDB-D):
  • Runs your Oracle databases on dedicated Exadata database servers and storage servers physically allocated solely to you within an OCI region. Think of it as single-tenant at the hardware infrastructure level, providing maximum isolation in the public cloud. You start with two database nodes and three storage servers.
• Exadata Database Service on Exascale Infrastructure (ExaDB-XS):
  • Runs your Oracle databases on the shared infrastructure of Exadata compute and storage resources within OCI. Exascale architecture decouples compute and storage for greater flexibility and elasticity. Consider it multi-tenant at the hardware infrastructure level, though your VMs provide logical isolation. Instead of dedicated database servers and storage, you get a dedicated Exadata cluster with dedicated CPU and Storage.

2. Key Differences and Decision Points:

3. When to Choose ExaDB-XS (Exascale Infrastructure):

• Cost Sensitivity: You need the power of Exadata but require a lower entry cost than dedicated hardware. Consolidate various smaller databases that demand high performance.
• Elasticity is Key: Your workload is variable or unpredictable, and you need the ability to scale computing resources up or down quickly and granularly.
• Starting Small: You are deploying a new application or migrating smaller workloads and want to start with a minimal footprint and grow later.
• Development & Testing: You need to rapidly provision/de-provision environments and leverage efficient database cloning (thin clones) for multiple developers or test cycles.  
• Simplified Storage Management: You prefer an abstracted storage layer (Exascale Vault) that does not require managing ASM allocations across specific storage servers.
• Physical Isolation Not Mandatory: Logical isolation provided by VMs on shared infrastructure meets your security and compliance needs.

4. When to Choose ExaDB-D (Dedicated Infrastructure):

• Maximum Isolation Required: Your security policies, compliance regulations (e.g., certain financial or government standards), or internal governance demand physically isolated hardware.
• Utmost Performance Predictability: You need guaranteed performance levels based entirely on your workloads running on dedicated, non-shared resources.
• Large-Scale Consolidation: You consolidate numerous or very large databases onto a powerful, isolated platform. If the database storage exceeds 90TB, ExaDB-D would be more cost-effective, irrespective of the ECPUs required.
• Migrating Existing Exadata: Moving a significant on-premises Exadata workload to the cloud requires equivalent dedicated resources.
• Specific Compliance: Regulations explicitly mandate single-tenant hardware, even within the cloud.

5. Price Comparison

With ExaDB-D, you get dedicated usable storage of 240 TB. This allows you to allocate up to 192 TB for databases (without local backup) or up to 96 TB with local backup. Taking just the storage vault cost for 90TB in ExaDB-XS almost matches the infrastructure cost for 2 database servers (up to 1520 ECPUs) and 3 storage servers (up to 240 TB usable space). So you cannot determine if ExaDB-D or ExaDB-XS will be price-performant just by looking at the ECPU requirement.

Let me show this with two sample Bill of Materials (BoM).  Since the blog template width is limited, here are the SKU descriptions used in the cost estimate.

Table 1: Large database storage footprint (90TB). ECPU allocation is very small, but ExaDB-XS is still expensive, and going with ExaDB-D makes it cheaper to scale.

Table 2: Smaller storage footprint (30TB). Plenty of ECPUs allocated on ExaDB-XS, still, it is cheaper than ExaDB-D.

In Summary, both ExaDB-XS and ExaDB-D offer the core performance and availability benefits of Exadata within OCI.

• Choose ExaDB-XS for elasticity, lower entry cost, smaller storage requirement and simplified management on shared infrastructure when physical isolation isn’t the top priority.
• Choose ExaDB-D for maximum isolation, larger database storage, performance predictability, and control on dedicated hardware, typically for mission-critical, large-scale, or highly regulated workloads.