VMware is working on a software-defined memory effort and thinks it could lead to the creation of “memory servers” – boxes full of memory that can be shared across a cluster.
DRAM can account for 40 per cent or more of a server’s cost, but remains expensive. Memory is also in demand, as more workloads require in-memory processing. VMware’s customers tell the company that access to memory is a bottleneck more often than access to I/O or storage.
VMware has also noticed that memory seems to be the last item of hardware that hasn’t been virtualised. The company considers forms of memory other than DRAM to be under-utilised by applications. In Virtzilla’s view that’s because today, software vendors need to write their own code to take advantage of different memory tiers.
The company therefore sees an opportunity to create an integrated memory service for applications and bake it into its flagship vSphere product.
Virtzilla’s worked on this under the code name “Project Capitola” for over two years, and in a VMworld session explained that its aim is to let applications access DRAM, CXL-attached memory or CXL-over-Ethernet, persistent memory like Optane, local NVMe and pooled NVMe as a pool of storage. vSphere will watch to detect the most active memory pages and place them on the tier of physical memory with the appropriate qualities.
Containers or VMs will be able to get just the memory they need. Software vendors won’t need to write their own tiering code – they’ll just need to make sure their apps are happy running as VMs or containers under vSphere. Most software vendors are there already.
Sudhanshu Jain, director of product management at VMware’s cloud product business unit, said Virtzilla’s already seeing interest from small cloud operators, who see the potential to offer a cheaper and slightly slower tier of services. Other buyers like the idea because it will let them decouple server and memory purchases – some are buying more DRAM than they need in anticipation of their databases growing.
Jain also suggested software-defined memory could even lead to the advent of “memory servers” – boxes filled with memory that is shared among the hosts in a cluster.
VMware admits that shunting work off into a memory tier other than DRAM will reduce performance, but by a manageable amount. It will also consume some more bandwidth within the datacentre.
If that gives you pause, VMware said its tests indicate total cost of ownership savings for hardware of between 30 and 50 per cent can be achieved. So perhaps that reduced performance will pay for itself because you won’t have had to pay for extra DRAM.
VMware hasn’t put a date on when this tech will debut, but is talking to the likes of Samsung, Intel, Micron, and top software vendors to make it a reality.
If this all seems fanciful, remember that it’s just seven years since VMware got serious about virtual storage in dedicated storage servers. In those far-off days, the idea of servers crammed with direct-attached storage as a replacement for SANs seemed odd. Yet virtual storage is now ubiquitous in the form of hyperconverged infrastructure.
VMware’s Jain said Dell and Cisco are also interested in Project Capitola, so bring on those storage servers. ®
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