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One of the big announces at the .NEXT Conference, was the introduction of erasure coding across nodes (in RAIN configuration) in Nutanix Operating System (NOS) version 4.1.3 (actually it’s a tech preview).

Nutanix Erasure Coding–X (EC-X) is a proprietary, native, patent pending, implementation of Erasure Coding. With EC-X, Nutanix customers are able to increase their usable storage capacity by up to 70%.

As written in a previous post, Erasure Coding (EC) is a way to implement data proctection in storage systems instead of using RAID techniques.

Erasure-CodingNutanix anyway wasn’t using RAID at all, they rely on a technology called Replication Factor (RF) that is is a quick and efficient technique of creating multiple (2 or 3) data copies across the cluster, making the cluster highly resilient with the ability to tolerate up to two simultaneous node (server) failures without downtime or data loss. It’s something similiar to a RAID10 (or RAID10 with double redoundandy) across nodes instead of across disks.

But it means that the space efficiency is 0.5 (50%) when using RF2 and it’s 0.33 (33%) when using RF3!

EC-X try to solve this problem, but keep still part the RF advantage: optimizes availability, provide with a faster rebuild, utilizes the entire cluster capacity.

Nutanix EC-X user case is data efficiency or capacity optimization, while keeping resiliency unchanged. Actually it’s not for datasets with predominantly overwrites and as suggested in the official site, for non-production environments (considering that it’s at a tech preview level).

It’s most effective on cold data (snapshots, file server, archives, backup sets).

As written the algorithm is a propietary, patent pending, optimized for the cost of operations. It’s a MapReduce based distribuited job.

Depending by the numbers of nodes (minimum is three, but the recommended configuration is with minimum 4 nodes) the space efficiency vary from 1.5 to 1.25. Starting from six nodes you reach the maxium level and data are not “striped” anymore to avoid high compunting penality


Most important, EC-X interoperates with all NOS features and can work in concert with dedupe and/or compressio.

See also:


Virtualization, Cloud and Storage Architect. Tech Field delegate. VMUG IT Co-Founder and board member. VMware VMTN Moderator and vExpert 2010-24. Dell TechCenter Rockstar 2014-15. Microsoft MVP 2014-16. Veeam Vanguard 2015-23. Nutanix NTC 2014-20. Several certifications including: VCDX-DCV, VCP-DCV/DT/Cloud, VCAP-DCA/DCD/CIA/CID/DTA/DTD, MCSA, MCSE, MCITP, CCA, NPP.