In order for an Exadata X9M-2 Elastic Rack to be installed, two power feeds are required for each of the three-phase 24kVA PDUs. A single cable from each PDU will not be enough to power the rack, and neither a splitter cable nor rearrangement of the power cables from the servers to the PDUs will be able to provide sufficient power for the system. Therefore, the installation cannot proceed until two power feeds are available per PDU.
For more information about power requirements for Exadata X9M-2 Elastic Racks, refer to the Oracle Exadata Database Machine X9M Implementation Essentials official text book and resources.
Search results: [1] Oracle Exadata Database Machine X9M-2 Full Rack Installation - Oracle Docs [2] Exadata Database Machine X8M-2 Mid-Size Rack Installation - Oracle Docs
https://docs.oracle.com/en/engineered-systems/exadata-database-machine/dbmin/exadata-site-requirements.html

High Capacity (HC) Storage Server: The Exadata X9M-2 HC storage server is configured with a combination of hard disks and flash memory, providing a balance of storage capacity and performance.
It includes 12 x 18 TB hard disk drives, which totals 216 TB of raw disk capacity.
For flash storage, it has 4 x 6.4 TB PCIe flash cards totaling 25.6 TB of flash storage. This configuration uses NVMe Flash Accelerator F680 cards optimized for database caching.
The persistent memory in the HC server totals 1.5 TB, enhancing performance for OLTP (Online Transaction Processing) workloads by providing ultra-fast access speeds compared to traditional flash storage.
Extreme Flash (EF) Storage Server: The EF storage server in the Exadata X9M-2 model is an all-flash storage server designed for high IOPS and low latency, making it ideal for performance-intensive workloads.
This configuration contains 8 x 6.4 TB PCIe flash cards, providing a raw capacity of 51.2 TB of high-performance flash storage.
In terms of persistent memory, it includes 756 GB of Intel Optane Persistent Memory. This enhances flash storage performance by offloading data processing directly to persistent memory.
The Exadata X9M-2 storage configurations-both HC and EF-are optimized for different workload requirements. The HC configuration caters to larger datasets needing high storage capacity, while the EF configuration is designed for workloads requiring high throughput and minimal latency.

The MS process on Exadata storage servers is natively endowed with REST services and these services are enabled by default. However, it is important to create appropriate roles and users to ensure security when accessing these services. This way, it is possible to disable ssh access to the storage servers, and still enable REST access to the MS process. It's not necessary to install Oracle Rest Data Services on each Database or Storage server or install the MS APEX application, the MS process on the storage servers already have REST services by default.

[1] Oracle Exadata Database Machine X9M Implementation Essentials Official Text Book [1][2], Chapter 4: Oracle Clusterware [2] Oracle Exadata Database Machine X9M Implementation Essentials Official Text Book [1][2], Chapter 8: Oracle Exadata Storage Server Software [3] Oracle Exadata Database Machine X9M Implementation Essentials Official Text Book [1][2], Chapter 9: Oracle Exadata Storage Server Infrastructure