Virtual SAN (VSAN) 6.0: What’s New

Virtual SAN 6.0

With VMware vSphere 6, Virtual SAN 6.0 also comes available. Virtual SAN 6.0 is the second version of VMware’s server side SAN solution. The most important improvements to the second version of VSAN are:

• Support for an all flash architecture;
• Major improvements on performance & scale – max 64 VSAN nodes per cluster, max 200 VMs per VSAN host, max 100K IOPS per host and a maximum VMDK size of 62 TB;
• New high performance snapshots & clones;
• Rack awareness to tolerate rack failures by using fault domains;
• Support for direct attached JBODs, especially useful in blade environments;
• HW based checksum & encryption.

Read on to get more details on this new version of VMware’s Virtual SAN.

New: Virtual SAN Architectures

Virtual SAN 6.0 offers two architectures different architectures:

1. Hybrid – Virtual SAN is using SSD disks/devices for caching and spinning disks (HDD) for capacity;
2. All Flash – Virtual SAN is using flash storage for both caching and capacity.

Read the table below for some more details on these two options:

In the case of All-Flash VSAN, flash storage responsible for caching will only do write caching and no read caching. It’s recommended to use high-grade flash based devices for the cache. You can use lower cost read-intensive flash based devices for capacity. In a Virtual SAN hybrid architecture the flash devices for caching will serve two purposes: 30% is used for a non-volatile write buffer, while 70% of the capacity is used for read cache.

With all the improvements, I am sure that VSAN 6.0 can now satisfy the needs of your most demanding business critical apps.

New: High Density Direct Attached Storage / JBOD

With the new High Density Direct Attached Storage (HDDAS) option it’s now possible to use VSAN in a effective way in blade environments. Both SSDs and HDDs are supported in a HDDAS configuration, as well in combination with local flash devices in the (blade) servers.

New On-Disk Format

Virtual SAN 6 introduces a new on-disk format to support higher performance characteristics and high performance snapshot & clones. If you want to make use of these improvements, an upgrade to the new on-disk format is required. The new on-disk format of VSAN 6.0  introduces a new VMDK type called vsanSparse.  vsanSparse based snapshots (as opposed to the redo log based snapshots in vSAN 5.5) are expected to deliver performance comparable to native SAN snapshots.

New: Proactive Rebalane

Another nice, new feature of VSAN 6.0 is proactive rebalance. Proactive Rebalance rebalances VSAN objects in case a new node is added to an existing VSAN cluster or in case disks are more than 80% full.

A Proactive Rebalance is performed through the Ruby vSphere Console.

New: VSAN Fault Domains

Fault Domains is a new VSAN feature that provides the ability to group multiple hosts within a cluster and define failure domains.

These new Fault Domains provide the ability to tolerate rack-, storage controller-, network- and power failures. In the future we might also be able to use the Fault Domains in a stretched cluster VSAN configuration, which is currently not yet supported. With the introduction of Fault Domains you can efficiently divide/place VSAN components in different racks / blade enclosures. An example is included in the next figure:

In this example four Fault Domains (FD) are defined, each rack is a FD. In this example the Failure To Tolerate (FTT) = 1, which means we need two copies and a witness. Because FD are used, the different VSAN components are all placed in the different FDs.

New Disk Serviceability Functions

VSAN 6 introduces some new disks serviceability functions:

1. Light LED on failures – The disk LED automatically turn on in case of a failure;
2. Turn on disk LED manually – Turn on a disk LED to locate a drive;
3. Marking a disk as local – If a disk is not detected as local disk, you can tag/untag the disk in the GUI;
4. Marking a disk as SSD – This option is now included in the GUI, if a disk is not recognized as an SSD device you can tag or untag it;

That’s it for now, to learn more about What’s New in vSphere 6 read this article.