FTF 011: vSAN and mixed storage policies

By | November 13, 2019

This post is a feature request for vSAN 🙂 One of my customers has a 4-nodes vSAN all-flash cluster. They use compression, deduplication and RAID 5 for non-critical VMs/vmdk and RAID 1 for critical. RAID 5 erasure coding requires less additional capacity to protect data than RAID 1 mirroring.

When you have vSAN enabled and you want to place the host in maintenance mode you have to choose one of the below options:

  1. Ensure accessibility
  2. Full data migration
  3. No data migration

My customer is not able to choose Full data migration because RAID 5 requires at least 4 hosts to be not in maintenance mode. This behaviour is correct. The 5th host requires additional license and hardware 😉

However, it would be a useful feature to have a possibility to choose and see which VMs can be still in compliance with a storage policy and accept or deny it. VMs on RAID 1 could be still in compliance but RAID 5 not (this would be accepted by my customer).

Simply put, Granular vSAN Maintenance Mode- e.g. Full data migration for RAID 1 and Ensure accessibility for RAID 5 - at the same time.

Useful resources

RAID 5 or RAID 6 Design Considerations

Using RAID 5 or RAID 6 Erasure Coding

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