vSAN - RAW Cluster capacity vs RAW capacity per host with FTT=1 or FTT=2

[kevincsf]

Hi there,

we have some questions about the raw capacity per host when designing a vSAN cluster in FTT=1 RAID1 with 5 hosts.

There is our examples :
Usable Capacity : 100GB (VM data)
FTT=1
RAID1
Number of hosts : 5
RAW Cluster Capacity : 200GB (100GB x 2) because of RAID1
What is the raw capacity per host ? Is that 200 / 5 = 40GB per host ?

Usable Capacity : 100GB (VM data)
FTT=2
RAID1
Number of hosts : 6
RAW Cluster Capacity : 200GB (100GB x 2) because of RAID1
What is the raw capacity per host ? Is that 200 / 6 = 33,33GB per host ?

Thank you your help.

Kevin

[depping]

So it is pretty straight forward, a VM which is 100GB will need:

RAID1 - FTT=1 = 100GB * 2 = 200GB

RAID5 - FTT=1 = 100GB * 1.33 = 133GB

Of course you will need to take things like "slack space / operational capacity" into account as well, but for RAID-5 the overhead is 33%, which means you multiply with 1.33 and for RAID-1 the overhead is 100%, which means you multiply by 2.