2 Replies Latest reply on Jun 24, 2019 10:21 AM by TheBobkin

    Streatched Cluster RAID 5

    MariuszKra Lurker


      I have infrastructure 3 + 3 + 1 (siteA SiteB Witness) vSAN 6.7 Streatched Cluster with RAID 1. We want to buy 2 servers one for each side.

      Can we change the raid 1 to raid 5? I find that RAID-5/RAID-6 is not supported in VSAN stretched clusters, it's true ?


      and whether with such a new solution 4 servers to the site with Raid 5,  is there a need to use a witness?



        • 1. Re: Streatched Cluster RAID 5
          daphnissov Guru
          vExpertCommunity Warriors

          If you're talking about the primary failures to tolerate (PFTT), then in a stretched cluster your choices are 0 or 1. Regardless, when you have a stretched cluster you still must have a witness as it's not optional.

          • 2. Re: Streatched Cluster RAID 5
            TheBobkin Virtuoso
            VMware EmployeesvExpert

            Hello Mariusz,


            Welcome to Communities.


            If you make your cluster a 4+4+1 you cannot RAID5 across the sites as that requires 4 Fault Domains - this isn't increased by adding more nodes, you still have SiteA + SiteB + Witness.

            With more nodes (at least 4 per site), you can use RAID5 local protection on each site (e.g. PFTT=1,SFTT=1,FTM=RAID5) - this does still require a Witness though.

            Also you could have just RAID5 pinned to one site (PFTT=0,SFTT=1,FTM=RAID5,Site=A/B) with only data on that site if you have data that doesn't require protection across sites - this doesn't require witness for data placement but the stretched cluster does of course still require a witness.