vSAN Space Efficiency Features

vSAN Space efficiency features such as: 

• Deduplication
• Compression 
• Erasure Coding

Reduce the total cost of ownership (TCO) of storage which are all features built directly into vSAN. Let’s go into each one a little more in-depth to learn how we’re saving money, storage and increasing performance at the same time.

Deduplication & Compression

Enabling dedup & compression can actually reduce the amount of physical storage consumed by almost as much as 7 times. For example, let’s say you have 20 Windows Server 2012 R2 VM’s and they have all their specific purpose (AD, Exchange, App, Web, DB, etc…). If we didn’t utilize de-dup and compression we would be holding the same set of data 20 times more than we need to.

Environments with redundant data such as similar operating systems typically benefit the most. Likewise, compression offers more favorable results with data that compresses well like text, bitmap, and program files. Data that is already compressed such as certain graphics formats and video files, as well as files that are encrypted, will yield little or no reduction in storage consumption from compression. Deduplication and compression results will vary based on the types of data stored in an all flash vSAN environment.
Note: Dedup and compression is a single cluster-wide setting that is disable by default and can be enabled using a drop down menu in the vSphere Web Client.

RAID 5/6 Erasure Coding

RAID-5/6 erasure coding is a space efficiency feature optimized for all flash configurations. Erasure coding provides the same levels of redundancy as mirroring, but with a reduced capacity requirement. In general, erasure coding is a method of taking data, breaking it into multiple pieces and spreading it across multiple devices, while adding parity data so it may be recreated in the event one of the pieces is corrupted or lost.

Unlike deduplication and compression, which offer variable levels of space efficiency, erasure coding guarantees capacity reduction over a mirroring data protection method at the same failure tolerance level. As an example, let’s consider a 100GB virtual disk. Surviving one disk or host failure requires 2 copies of data at 2x the capacity, i.e., 200GB. If RAID-5 erasure coding is used to protect the object, the 100GB virtual disk will consume 133GB of raw capacity—a 33% reduction in consumed capacity versus RAID-1 mirroring.
RAID-5 erasure coding requires a minimum of four hosts. Let’s look at a simple example of a 100GB virtual disk. When a policy containing a RAID-5 erasure coding rule is assigned to this object, three data components and one parity component are created. To survive the loss of a disk or host (FTT=1), these components are distributed across four hosts in the cluster.

RAID-6 erasure coding requires a minimum of six hosts. Using our previous example of a 100GB virtual disk, the RAID-6 erasure coding rule creates four data components and two parity components. This configuration can survive the loss of two disks or hosts simultaneously (FTT=2). While erasure coding provides significant capacity savings over mirroring, understand that erasure coding requires additional processing overhead. This is common with any storage platform. Erasure coding is only supported in all flash vSAN configurations. Therefore, the performance impact is negligible in most cases due to the inherent performance of flash devices.

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