slack space for 3-Node vSAN cluster

[suhag79]

Hi all,

We are going to setup 3 Node vSAN cluster with essential plus licensing. All three nodes will be installed in remote office and vCenter essential appliance will be part of the same 3 Node vSAN cluster. 

Total 15 Vms are going to be host and storage requirement for these VMs are 10 TB. We will be setting up RAID-1 and FTT-1 policy so storage requirement will be 10 TB*2 = 20 TB. I want to know, since this is 3 node vSAN cluster, should i consider 30% slack space for the component rebuild ? i guess No ?

Thanks,

[suhag79]

Hello all,

Can anyone help on this. Should we consider slack space in storage sizing for 3 Node vSAN cluster ?

Thanks,

[TheBobkin · Accepted solution]

Hello suhag79​

"I want to know, since this is 3 node vSAN cluster, should i consider 30% slack space for the component rebuild ? i guess No ?"

Always consider slack space - even if you are never planning on changing Storage Policies in such a way that they will need a lot of resync space (e.g. changing the Stripe Width), you will inevitably require some space for resyncs following maintenance/upgrades/updates of single nodes.

The more important thing to consider here is slack space to recover from a single disk/Disk-Group failure - if you have no space to rebuild data on this node then your data is FTT=0 and you also won't be able create new FTT=1 Objects until you get this fixed.

Additionally allowing some slack space for growth and expansion is generally a better option than waiting until you are out of space and facing the issues that come with this to add more storage.

Bob

[suhag79]

Thanks TheBobkin

Appreciate  the info.