ESXi 5.0 installations use GUID Partition Tables (GPT) instead of MSDOS-based partitioning called MBR. New Installation creates several partitions like Bootbank Partitions, Diagnostic Partition, Scratch & VMFS partition on disk.
Below Image refers to ESXi5 Partitioning details:
- MBR : This 4MB partition is used for booting the system and locating the Bootable Kernel images of Hypervisor. This MBR actually points to files present in Primary Bootbank or sometimes Secondary Bootbank.
- Primary Bootbank: This 250 MB size Bootbank will have active image of Hypervisor. When System boots up, MBR actually looks for file present in this bootbank hence its called primary bootbank. Actual Hypervisor image is compressed file and gets decompressed on boot and contains ESXi Operating system.Below is the screenshot of files present in bootbank partition.
3. Secondary Bootbank: This 250MB size partition is empty at the time of fresh installation of ESXi. This partition comes into the picture only when doing ESXi upgrade. This partition also contains full active system image and used as fail-safe for applying updates. If any problem occurs during upgradation process, an administrator can manually intervene at boot time to choose secondary boot bank image for successful boot.
This Dual boot bank architecture of ESXi makes admin life easy to avoid any boot failure even though upgrade process fails.
4. Dump Partition: This 110 MB size partition is also called as “Diagnostic Partition” or “CoreDumpPartition”. This coredump partition stores all the diagnostic information during PSOD ( purple screen of death) or Host failure. This information is significantly important for developers to troubleshoot the issue caused PSOD.
5. Store Partition: This 285 MB partition contains all the VMware-Tools ISO images for operating systems.
6. Scratch Partition: This 4GB VFAT scratch partition created to store vm-support output bundle. This bundle collects all the required logs like vmkernel log, hostd, vpxa etc… required for debugging. All the Hypervisor related log files gets stored under this partition.This partition is not at all mandatory. In absence of this partition all the log files and vm-support files will be stored In ramdisk which required good amount of memory installed in system.
In Low-memory situations, Its recommended to create a scratch partition if its not present.
Below is the snippet of scratch partition
Note: To create the VMFS and scratch partition, the ESXi installer requires a minimum of 5.2GB of free space on the installation disk.
Layout of ESXi5 Partition table
As mentioned earlier, Overall size of ESXi kernel image is 900MB excluding scratch and VMFS partition.
Execute “ls –lh /dev/disks” command to list all the partition created on ESXi Installer disk
let’s go over each partition one by one
- 690b11c015a69f0018aa997e4038073b -> 150.G
This naa id represent ESXi Installer disk where ESXi installed and overall disk size consumed by ESXi during installation. In above example, ESXi consumed 150GB disk space.Let’s dig into space consumed by each partition during ESXi Installation
- 690b11c015a69f0018aa997e4038073b:1 -> 4.0M
- This naa id: 1 presents 1st partition created on disk of 4MB size known as MBR or boot partition.
- 690b11c015a69f0018aa997e4038073b:5 -> 250.0M
- This naa id:5 represent 5th partition created on disk of 250MB size known as Primary Bootbank.
- 690b11c015a69f0018aa997e4038073b:6 -> 250.0M
- This naa id:6 represent 6th partition created on disk of 250MB size known as Secondary Bootbank
- 690b11c015a69f0018aa997e4038073b:7 -> 110.0 M
- This naa id:7 represent 7th partition created on disk of 110MB size known as Core Dump Partition
- 690b11c015a69f0018aa997e4038073b:8 -> 286.0M
- This naa id :8 represent 8th partition created on disk of 286MB size known as Store partition.If we add up the size of all these partitions, it comes 900MB so above mentioned theory proved.
- 690b11c015a69f0018aa997e4038073b:2 -> 4.0G
- This naa id:2 represent 2nd partition created on disk of 4GB size known as scratch partition.
- 690b11c015a69f0018aa997e4038073b:3 -> 145.1G
- This naa id:3 represent 3rd partition created on disk known as VMFS partition and it claims all the disk space available on the disk ( 145.1G in above example)