VSAN vs. Traditional Storage

The VMWare VSAN is getting a lot of hype and is an exciting technology. It allows a datacenter to leverage local storage in ESXi hosts without needing a traditional shared storage device such as an EMC or NetApp SAN (among many other vendors).

The VSAN product is geared toward mid-market organizations and up that have an SDDC (Software Defined Data Center) strategy. It is typically not a cost effective solution for SMBs. Above is a graphic that shows how the storage is pooled leveraging hard drives in each host.


VSAN is currently at version 1.0 and 2.0 is promised to be included when vSphere 6 is released (TBD). Along with the networking component, NSX, VMware is sure to gain marketshare in the SDDC space in 2015.

VSAN Requirements

I thought the below requirements and intangibles were the most interesting for VSAN:

  • $2500 list per CPU socket and is sold separately from vSphere
  • Minimum 3 hosts
  • Minimum ESXi host licensing is Essentials Plus and above (Essentials Plus kits come with 3 licensed hosts and vSphere)
  • Dedicated 1 Gb NICs required (10GB recommended)
  • Multicast must be enabled on the VSAN VLAN
  • Minimum 1 HDD and 1 SSD on the first 3 hosts
  • Additional hosts above the base 3 can run VMs accessing storage on the other 3 hosts without any local hard drives.
  • The VSAN licensing includes the vSphere Distributed Switching feature even if running on Essentials Plus, Standard or Essentials (vDS comes with only Enterprise Plus by default).
  • Maximum of (35) hard drives per host (consider HP's 25-drive SFF model)
  • All non-SSD drives must be the same across all slots and hosts for consistent IO (no tiering). The option of using 10K vs 7.2K drives is left up to being a design choice.
  • Recommend ratio of 1:10 of SSD to HDD capacity
  • SSDs provide read and write caching in a 70/30 ratio.
  • A separate file share or NAS is required for syslogs as they cannot reside on SD cards or the VSAN storage.
  • No dedupe
  • VSAN v2.0 (coming in vSphere 6) has a new disk format that allows for efficient and scalable snapshots.

Below is an example configuration that would provide about 16.0 TB of usable capacity and loosely 60,000 IOPS with about 5% of capacity as SSD. The costs will go up or down from here based on various design choices:

10 3 2014 11 21 39 AM 

Compare the cost, benefits and history against traditional arrays such as EMC and NetApp. One major benefit of VSAN is the policy based management applied to VMs. It provides a much easier and more intuitive way to prioritize the performance of applications. The VSAN is also slated to be easier to administer and expand with less specialized storage knowledge required. I'm looking forward to seeing the full feature list of VSAN 2.0 when it is released along with vSphere 6.0 which I'm sure the EMC and NetApp marketing and sales team will have their eye on as well. Have a question for Todd? Email us at .

Author: Todd Bey


  • VSAN storage calculator on the Yellow Bricks blog here.
  • Hardware list of VSAN-ready nodes here.
  • VMware Blog discussing the VSAN multicast requirement here.

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