Exadata Cloud@Customer X8M: The Best “In Datacenter” Database Cloud Platform

On July 8, perhaps a bit lost among the excitement of Autonomous Database on Exadata Cloud@Customer and Dedicated Region Cloud@Customer, Oracle announced availability of Exadata Cloud@Customer X8M. Oracle Exadata X8M was announced back at OOW 2019, along with Gen 2 Exadata Cloud@Customer. Many would have thought that meant Gen 2 Exadata Cloud@Customer was built on Exadata X8M, but it was not. Rather, until now, Gen 2 Exadata Cloud@Customer was based on Exadata X8, the second-best database platform on the planet. For those of you waiting for Exadata Cloud@Customer to support the latest Exadata technology, your wait is over.

What’s the big deal about a letter being added to the model number—after all, both have the same CPUs, memory, and storage? Those components stay the same, but Exadata X8M boosts its interconnect fabric from a 40Gb/sec InfiniBand Network to a 100Gb/sec Remote Direct Memory Access (RDMA) over Converged Ethernet (RoCE) network. It also upgrades the Xen hypervisor technology to the more popular Kernel Virtual Machine (KVM). In addition, Exadata Cloud@Customer X8M almost doubles the usable memory in each database server, and Oracle Exadata X8M adds 1.5TB of persistent memory (PMEM) to each storage server. 

As with many things Exadata, it is the software innovation and how Oracle uses industry standard hardware components that truly differentiate Exadata from other solutions. Exadata X8M uses PMEM as a new tier of storage in the storage servers, maximizing its benefit by allowing it to be shared by all databases in the platform, and improving its HA characteristics in the event of a failure. More importantly, Exadata exposes PMEM as memory modules, enabling database clients to use RDMA to access the data in PMEM directly over the network, without any involvement from the OS or network stack on the storage cell, dramatically reducing latency by 10x for sensitive operations like database reads and commit log writes.

The magic software is the “Data Accelerator” and “Commit Accelerator,” features that speed up data reads and commit writes, respectively. To appreciate the importance of the Exadata approach to using PMEM, we need to look at a few numbers. The latency to read an 8K database block from a network-attached NVMe device is around 190usec, with about 100usec of the time spent sending the block across the network. PMEM is about 10x faster than flash, so simply replacing flash with PMEM, significantly drops the device read latency. However, most of that improvement is masked by the 100usec network latency. To realize the benefit of PMEM’s speed, we need to eliminate most of the network latency. Exadata X8M does that using RDMA. RDMA bypasses the OS and network stack, enabling the NIC on the remote database server to directly read and write to the memory location on the storage server. The result is an average of 19usec to read that same 8K block, 10x faster than before. The Commit Accelerator provides a similar benefit to latency-sensitive commit writes to the REDO logs.

The result of these accelerators is improved response time for OLTP applications, that will spend less time waiting for data and commit acknowledgements. The 2.5x faster RoCE network will allow data warehouse and analytics applications to send more data more quickly to the database servers for processing, and the doubling of memory in the database servers will allow for more databases in a single rack. Overall, these enable higher consolidation levels that in turn lowers TCO.

Exadata Cloud@Customer X8M will outperform any on-premises storage arrays, even those using PMEM, due to its smart software and RDMA access directly from the database.It is hardly even worth comparing to other cloud solutions. AWS, with their network attached flash storage, promises 1msec access to data, over 50x slower.

So, if you’re interested in moving to a Cloud business model, but need to keep the data local, and want to get the same performance available on the best on-premises database platform, Oracle Exadata X8M, you should look at Oracle Exadata Cloud@Customer X8M—the best “in datacenter” database cloud platform is now even better.