VMware going to Capitola for memory tiering

VMware is developing vSphere software to virtualise different kinds of memory into a single logical tier, so that applications can have access to more memory than there is DRAM in their host physical server without having to use different coding methods.

The initiative is called Project Capitola and was revealed as a technology review at the VMworld 2021 event. It is discussed in a VMware blog by the vSphere team. It is, they write, “a software-defined memory implementation that will aggregate tiers of different memory types such as DRAM, PMEM, NVMe and other future technologies in a cost-effective manner, to deliver a uniform consumption model that is transparent to applications”.

The developing CXL interconnect has a role to play as a blog diagram shows:

We see pools of different kinds of memory: DRAM (DDR), CXL-attached Optane persistent memory (DIMMs)  and other “memory” accessed via CXL, RDMA-over-Ethernet (RoCE), NVMe — which must surely mean SSDs — and pooled NVMe. More than one physical server can be involved in this memory tiering and logical pooling, according to the diagram.

The pooled memory types will form a non-uniform memory architecture (NUMA) with different tiers having different access speeds. That will have to be managed by the Project Capitola software.

VMware is working with:

  • Memory vendors such as Samsung, Micron and Intel — memory here meaning DRAM and Optane and possibly Samsung’s Z-SSD;
  • Server vendors such as Cisco, Dell, HPE, and Lenovo;
  • Service providers — Equinix.

You can read VMware partner comments and here is a sample of them:

  • Cisco CTO Dan Hanson — “We are excited to partner with VMware on Project Capitola to further enhance the hybrid cloud vision we have with UCS, HyperFlex, and Intersight by including this software-defined memory management into our set of solution offerings.”
  • Dell chief technology & innovation officer Paul Perez — “With tiered memory technology from VMware on Dell EMC PowerEdge servers, we’re able to increase capacity and performance for memory-intensive workloads.”
  • Hazelcast chief product officer Manish Devgan — “Hazelcast is excited to partner with VMware on Project Capitola to deliver a flexible, simplified software defined memory management solution that brings together historical and real-time data at microsecond latencies to empower innovative applications.”
  • Micron senior director of the datacentre segment Ryan Baxter — “Project Capitola can deliver new levels of memory access to data-hungry applications, enabling customers to optimise for solution performance and performance per dollar. As an industry leader in DRAM and NAND technology, we are delighted to work with VMware to deliver this value to customers.”

It will be interesting see what Micron brings to the Capotola table as it exited its 3D XPoint partnership with Intel in favour of developing its own CXL-accessed memory products.

VMware says its leading partner is Intel and Capitola will come to the market, possibly in a first phase, using Xeon processors and Optane persistent memory. Trust Intel to support this idea.

If one hypervisor can abstract different tiers of memory into a single virtual tier then so can another — and we expect Nutanix’s AHV and other KVM versions such as Red Hat to do so as well. And if a hypervisor can do it then why not an operating system?