Tech Chronicles

VMware vSan Capacity Sizing

You will naturally like to see what equipment you need and what enhancements you can make with these needs before you invest for a new vSan Environment

There are several manufacturer tools that I share links with below that you can perform automatically.

Click here for vSan Readynode Sizer and here for Vxrail Xpress Sizer.

So what should you do if you want to do an average calculation without having to depend on these tools?

Let’s say the capacity you need is 10 TB;

We must multiply this capacity by the following coefficients, depending on the type of RAID desired. As I mentioned in the my previous article here, RAID types in vSAN environment maybe implemented as Datastore Default, per-VM and pervmdk. So when you do these calculations put you will have X VM RAID, 5x VM RAID5 into account to achieve more accurate results.

RAID coefficients;

RAID1 = 2 (Min. 3 server or 2 servers and Witness node)

RAID5 = 1.33 (Min. 4 Server and All-Flash)

Raıd6 = 1.25 (Min. 6 server and All-Flash)

Let’s say we have 10TB net capacity requirement with RAID1 and all-flash. Only the All-Flash environment supports Deduplication and Compression feature.

10TB x 2 = 20TB

Deduplication & Compression coefficients can be used between 1.5 and 2 depending on the data type. This property is an achievement unlike the raid, so the value obtained in the previous calculation is divided into this coefficient.

Consider it 1.5, given that the data is not well to be deduped and compressed.

20TB/1.5 = 13.33 TB

It is not recommended to fill the vSAN environment more than 70%, so 30% Slack Space must be added just incase on the calculated capacity. (The tests I made in the test environment continued to operate  even in 95% of the capacity. Testing in Production environment is not recommended!)

13.33 tb x 1.30 = 17.33 TB

Considering that capacity is intended to be used in three servers;

17.33 TB/3 = 5.78 TB The capacity needed per server is needed.

This 5.78 TB capacity can be supplied with discs of various sizes according to the need.

More than 1 disk group having more than 1 capacity disks are recommended for both security and performance reasons.

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