1 Reply Latest reply on Jul 6, 2020 1:52 PM by vFouad

    vSAN 6.6.1 - adding capacity disk to a host where deduplication/compression are enabled

    dsiedlak Lurker

      Dears,

      I've following setup: vcenter/ESXi 6.5 & vSAN 6.6.1. ESXi hypervisors are guesting two disk groups each, all SSD. Last time I've done some scaling by adding capacity disks. Now I found very disturbing information related to vSAN 6.6.2:

       

      vSAN: Adding and Removing Drives with Deduplication and Compression

      "Note that when a drive is added to a disk group with deduplication and compression enabled, the newly added drive does not automatically participate in the deduplication and compression process. The new drive is used to store data, but that data is not deduplicated and compressed. The disk group must be deleted and recreated so that all of the capacity drives in the disk group (including the new drive) store deduplicated and compressed data."

       

      Is that true for vSAN 6.6.1 and later? If yes, should I need to take the following steps?

      • place the host in maintenance mode with 'evacuate all data to the other hosts' (long process...),
      • delete and recreate disk groups one by one,
      • exit maintenance mode & proactive re-balance it.

       

      Thank you,

      Dominik

        • 1. Re: vSAN 6.6.1 - adding capacity disk to a host where deduplication/compression are enabled
          vFouad Hot Shot
          VMware EmployeesvExpert

          That is the correct process; if you want dedup&compression on all he disks in the disk group.

          You missed step 0 though...

          Have current and tested backups of all critical information; then:

           

          • place the host in maintenance mode with 'evacuate all data to the other hosts' (long process...),
          • delete and recreate disk groups one by one, (ensure that dedup and compression is enabled on the disk groups).
          • exit maintenance mode & proactive re-balance it.  

           

          If you miss the re-balance that is ok, when you put the next host in to Maintenance mode (assuming you are adding a disk to all hosts for a homogenous environment) it will take advantage of the space on the empty host. The pro active rebalance should only necessary after completing work on the last host.