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Understanding Virtual SAN
By Pranay Jha | Apr 19, 2016 | In Articles | Update: Apr 22, 2017 | Total Views [ 1293 ]
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Overview of VSAN:-

  • VSAN pools the locally attached storage from members of a VSAN–enabled cluster and presents the aggregated pool back to all hosts within the cluster.
  • It has multiple disks presented to multiple hosts
  • VSAN does not require any additional software installations.
  • It is built directly into ESXi itself. Managed from vCenter Server.
  • VSAN is compatible with all the other cluster features that vSphere offers, such as vMotion, HA, and DRS.
  • We can even use Storage DRS to migrate VMs on or off a VSAN datastore.
  • VSAN uses the disks directly attached to the ESXi hosts and is simple to set up.
  • VSAN uses the concept calling RAIN, or reliable array of independent nodes.
  • VSAN uses a combination of vSphere APIs for Storage Awareness (VASA) and storage policies to ensure that VMs are located on more than one disk and/or host to achieve their performance and availability requirements.
  • VMware recommends 10 Gbps networking between ESXi hosts when using VSAN.


Requirements for VSAN:-

  • ESXi 5.5 or newer hosts
  • vCenter 5.5 or newer
  • One or more SSDs per host
  • One or more HDDs per host for hybrid mode
  • Storage controllers must be on the VSAN HCL
  • Minimum of three hosts per VSAN cluster
  • Maximum of 64 hosts per VSAN cluster
  • 1 Gbps network between hosts (10 Gbps highly recommended)


Types of VSAN Configuration

  • Hybrid
  • All SSD(Flash Only Disconnect)



It uses both SSD and magnetic hard disks.
VSAN requires at least one flash-based device in
each host.
Hybrid VSANs use the SSD as a read and write cache just as some external SANs do.
W hen blocks are written to the underlying datastore, they are written to the SSDs first, and later the data can be relocated to the (spinning) HDDs.
VSAN’s read/write cache ratio is 70 percent read, 30 percent write.

            All SSD:

 It uses all SSD Disks.

Source: Scott Lowe's Mastering vSphere 6.0


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Pranay Jha
Pranay Jha
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Thank you for visiting my profile. I am Pranay Jha, bring along a total of 11+ years of extensive experience with me in Information Technology sector for organizations from small business to large enterprises, wherein my current assignment I am associated with IBM as a Technical Solution Architect for Virtualization platform. I am vExpert x 3 (16/17/18), VCIX-DCV, VCAP5/6-DCD, VCAP5-DCA, VCP7-CMA, VCP5/6-DCV, VCA-DCV, VCA-Cloud, VSP, VCE-CIA, MCITP, MCSE, MCSA(Messaging). I am also an Independent blogger and founder of and I can be reached via email at or Direct Message via Contact Us form.

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