ESXi Partition - Lets break it down!

I bet you have installed ESXi multiple times by now, have you ever noticed that we do not get any option to modify the partition layout? this is because ESXi Partitions are automatically set by the installation process. 

Quick run thru on the history, Once upon a time, long before the coming of ESXi and when there was only ESX. Taking into account the native behavior of Linux architecture in addition to the ESX specific characteristics, partitioning best practices evolved. While not every administrator will agree on the exact size a given partition should be, a pattern in how ESX is properly partitioned is fairly evident, plus or minus the partition size variance that fits the personal taste of the administrator or perhaps company baseline policies or standards. Right there is a good a reason as any to partition manually ,hence Partitioning became Automatic while installation.

Now let us take a deep dive, First of, What are the ESXi partition, take a look a the below picture.

ESXi partitions description :

    Partition 1: systemPartition -> Bootloader Partition (4MB )  -> This Partition is needed for Booting

    Partition 5: linuxNative  -> /bootbank (250MB)  -> The hypervisor image is located on this Partition

    Partition 6: linuxNative -> /altbootbank ( 250MB) -> After ESXi upgrade, the current image is copied from the bootbank partition.

    Partition 7: vmkDiagnostic  -> First Diagnostic Partition (110MB) -> For PSOD crash.

    Partition 8: linuxNative  -> /store (286MB) -> This is the product locker which contains the VMtools.

    Partition 9: vmkDiagnostic -> Second Diagnostic Partition ( 2.5 GB) -> This is the vmkDiagnostic partition

    Partition 2: linuxNative  -> /scratch (4GB) -> This is for the ESXi logs ( non-presistant)

    Partition 3: VMFS datastore -> For datastores ( only created if installation is done on non-flash memory)

The partition table format is GPT from 5.x and previously it was traditional MBR table.

How to find the partition details on an ESXi:

First get the disk on which the ESXi is installed, you can run # ls /dev/disks -lh to get the disk details. Then you can use # partedUtil  getptbl /disk -> this will give an output like the below:

Why do I have to know about ESXi partitions:

You get a better understanding of the ESXi configuration and also while troubleshooting based on PSOD crashes, Scartch partition setup or while consulting customers on best practices these information would give you a hand. Also you can be confident when you know which partition is used for which operation.  

Quick links - https://blogs.vmware.com/feed-items/esxi-6-56-x-partition-layout

https://blogs.virtualmaestro.in/2017/04/esxi-656x-partition-layout.html

Article which i referred - https://www.vmwarearena.com/what-i-wish-everyone-knew-about-esxi-partition/