KumoScale adds online data migration to its storage bow

Kioxia America has added online data migration to its KumoScale flash box, to allow continued application access to data in drive maintenance windows.

Joel Dedrick, Kioxia America’s VP and GM for networked storage software, said in the launch announcement: “For mission-critical applications, downtime due to maintenance can be extraordinarily costly. Eliminating the need for maintenance windows is just one of the ways that we help our customers maximise the returns on their data centre investments.”

KumoScale storage software is based on NVMe-over Fabric and manages a JBOF (Just a Box of Flash), containing Kioxia NVMe SSDs. The commodity hardware array is made by Kioxia’s partners. Kioxia calls the result ‘software-enabled flash technology’.

The new features include online volume migration, in which a set of data is replicated from one SSD to another. Migration may be needed to reduce the IO load on the source drive or perform maintenance or to even out write access wear across a set of drives. The target SSD can be in the same KumoScale node or a connected one.

Kioxia America graphic

Normally, migration involves taking a drive offline and sending the volume to the target drive while it is disconnected from online access. Important applications may be quiesced or left waiting during this process.

With KumoScale’s online migration, write accesses to the source drive are redirected to the target drive while read accesses are left undisturbed. The volume data is moved across to the target drive. When migration is complete, read accesses to the source drive are remapped to the target drive and the source drive can be taken offline. There is no interruption of online access to the data volume during the process. 

Kioxia is actively adding features to KumoScale:

  • May 2020 – Thin provisioning added
  • April 2020 – snapshots and clones added
  • February 2020 – resilient provisioner service to map physical drives and nodes to host requests
  • September 2019 – support for Graphite and Prometheus telemetry frameworks
  • March 2019 – NVME-oF transports extended with TCP/IP on top of RoCE

Online migration now caps this list and expands KumoScale use cases to mission-critical apps that can’t suffer downtime.


Kioxia has made the KumoScale API available via GitHub. The company said the API combines software flexibility, host control and flash native semantics to make flash easier to manage, quicker to deploy and more predictable in its behaviour.

With Kumoscale, host applications access data in flash storage using the API and so avoid accessing actual SSDs. The physical SSDs are virtualized by the API. This means the technology inside them can change without mandating change in the accessing applications.

The API also facilitates global wear management across the SSDs in a KumoScale box and can enable more consistent latencies by levelling out IO accesses across a population of drives.

Eric Ries, SVP for Kioxia America’s memory storage strategy division, provided this take: “We want the cloud computing and storage development community to benefit from all that this new technology has to offer. It opens the door for hyperscale storage developers to unleash the full potential of flash in their unique environments in a way that just isn’t possible with traditional storage methodologies.”

This ability for host server software to manage flash drive behaviour is a feature of Western Digital’s zoned flash drive initiative. Western Digital and Kioxia jointly operate NAND foundries making SSD chips.

The KumoScale API specification is available on the Kioxia America GitHub repository.