Exadata X8M introduces BIG Architectural Changes

Launched at the 2019 Oracle Open Word Conference the Exadata X8M introduces few big architectural changes which make the leading Oracle Database Machine even more attractive.

Among the most relevant changes there are:

  • InfiniBand Network replacement with an Ethernet network fabric
  • Intel Optane DC Persistent Memory inside the Storage Cell
  • New Remote Direct Memory Access (RDMA) functionalities
  • Replacement of the XEN Hypervisor with KVM

InfiniBand Network replacement with an Ethernet network fabric

The characteristic 40Gbit/second InfiniBand network used for all private network communications among database nodes and storage cells has been replaced by a new 100Gbit/second RDMA over Converged Ethernet Fabric (RoCE) based on the Cisco Switch 9336c RoCE .

The new network not only increase 2.5x the throughput but also reduces the communication latancy.

The schema below highlight the network architecture change for all private communications

Intel Optane DC Persistent Memory inside the Storage Cell

Oracle has introduced 1.5TB of Intel Optane DC Persistent Memory as additional storage device inside all Exadata X8M Storage Cell, (no matter if equipped with HC and EF devices), and it is used as accelerator in front of the Flash Memory Cards. In term of speed this new type of ultra fast storage device is located between the DRAM and the Flash Memory, bringing to three the number of multi-tiered storage devices present inside the Storage Cell.

The Exadata unique software is than capable to extract the maximum performance from this HW configuration, automatically detecting and placing the hottest data on the Persistent Memory, reducing the I/O latency of the most critical tasks.

Below is described the list of Storage Cell’s devices ordered by speed.

New Remote Direct Memory Access (RDMA) functionalities

Until now the RDMA was used among database nodes for exchanging Exafusion messages or for Smart Fusion Block Transfer. Starting with Exadata X8M, the RDMA technology is also used to perform direct I/O access to the Persistent Memory of the Storage Cells, bypassing the network and I/O stack and eliminating expensive CPU interrupts and context switches. This optimization reduces the latency by 10x, from 200μs to less than 19μs.

The picture below highlight the “Database Node to Database Node” and the new “Database Node to Storage Cell” communication using RDMA functionalities.

Replacement of the XEN Hypervisor with KVM

Oracle virtualization technology is called Oracle Virtual Machine (OVM) and in a productive invironment it can be implemented with one of this two different products:

  • Xen
  • KVM

Starting with Exadata X8M-2 the virtualization technology in use is KVM instead of Xen. Oracle started replacing Xen with KVM few years ago, for example on the smaller engineered system ODA X7-2M & X7-2S, but for the Exadata took longer, and I think the root cause was the InfiniBand network. Infact KVM is not fully integrated with InfiniBand, and it does not support bridging.

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