VSAN Usable Storage in this Case 5TB

[jgover]

Hi,

Trying to figure out the algebra on why 21 1TB drives are required in total across 3 Hosts for RAW storage capacity of 5TB  that I choose from the VSAN guide below.

So that is 7 disks in each server.

VMware Compatibility Guide - vsan

	Vendor	Model	Profile & Capacity

DELL

HY-4: DELL R630

Ready Node Generation: Gen2 - 12G Profile: HY-4 Series Raw Storage Capacity: 5 TB

Click here for Ready Node Model details : HY-4: DELL R630

Components	Details	Quantity
SKU	Contact Dell Sales Rep
ESXi Pre-Installed?	Yes
System	PowerEdge R630	3
CPU	Intel® Xeon® E5-2640 v4 2.4GHz,25M Cache,8.0GT/s QPI,Turbo,HT,10C/20T (90W) Max Mem 2133MHz	6
Memory	16GB RDIMM, 2400MT/s, Dual Rank, x8 Data Width	24
Caching Tier	400GB Solid State Drive SATA Write Intensive 2.5in, SM865	3
Capacity Tier	1TB 7.2K RPM NLSAS 6Gbps 2.5in	21
Controller	DELL PERC H730 Adapter SAS-RAID	3
NIC	Intel X520 DP 10Gb DA/SFP+ Server AdapterIntel X520 DP 10Gb DA/SFP+, + I350 DP 1Gb Ethernet, Network Daughter Card	3
Boot Device	Internal Dual SD Module (IDSDM) 2 x 8 GB SD cards)	3

Supported Releases

ESXi 6.0 U2, ESXi 6.0 U1

- See more at: https://www.vmware.com/resources/compatibility/search.php?deviceCategory=vsan#sthash.Qdd5TFOt.dpuf

[depping]

I guess that is a mistake. RAW storage is 21TB, usable will depend on FTT chosen and some other things like spare capacity / growth etc

[jgover]

Yes that original VSAN site was buggy.

I generally go with the this now:

https://code.vmware.com/virtual-san-design-and-sizing-guide#Cluster Capacity

1.5.5 Usable Capacity

Virtual SAN usable capacity is the amount of capacity that can be used to store the VMDK files of all virtual machines. It is determined by subtracting the Virtual SAN overhead from the disk capacity and then dividing the remaining amount by the number of failures to tolerate plus 1:

• Formula: (DiskCapacity – DskGrp x DskPerDskGrp x Hst x VSANoverhead )/(ftt+1)
• Example: (1,104,000GB – 280GB)/(ftt+1) = 1,103,720GB/(2) = 551,860GB Usable Capacity

Usable always seems to work out to roughly half to RAW.

P.S. I know you know this stuff inside out. Just posting back for general public.

Thanks

Jeff