In this article we will look at the partition layout of ESXi 5. A change from earlier ESXi 4.x is that the older MBR partitioning system is replaced with a GPT style partition table. The first five partitions are mandatory and consumes exactly 900 MB together, while the last two is not technically necessary.
The first small partition is just for booting the system and locating the hypervisor image which could be on one of the next two partitions.
The actual system image is located on the first 250 MB partition, formatted with plain old FAT. The image itself, s.v00, is a 124 MB compressed file, which is decompressed on boot and contains the hypervisor operating system.
The next 250 MB FAT partition is used for inplace upgrades and is empty at start if a clean installation was done.
If the hypervisor itself should crash (“purple screen of death“) the 110 MB core dump partition is used for dumping crash information.
In this 286 MB partition we have mostly ISO files with the VMware Tools for the various supported guest operating system. We can also find the floppy images for the PVSCSI virtual disk controller, if in need to use these directly at installation on Windows Server guests.
If installing ESXi on a local hard drive and this drive is larger than about 5 GB a “scratch” partition will be created. This partition holds mostly the various log files for the vmkernel and other components. If installing on a very small drive, about 1 GB, or on USB, this scratch partition will be missing and the log files will be in RAM only. This means that in the case of power failure the log files will be lost.
A partition formatted with VMFS will be automatically created on the rest of the space of the install drive. In ESXi 5.0 the new VMFS 5 will be used with a standard block size of 1 MB no matter the size of the disk and better support for small files, e.g. VMX configuration and log files. When now using GPT (Guid Partition Table) we could also use disks with sizes over 2 TB.
If using the ESXi Shell you can access the different partitions through file system mounts. For example, the directory /bootbank is the first 250 MB partition where the actual hypervisor files are located. The /store directory is the 286 MB large repository for VMware Tools and other files.
The compressed image in the first 250 MB “boot bank” partition is larger in 5.0 than in 4.1, (where the image was 70 MB), but still a very small disk foot print with about 124 MB in 5.0. If you later update the active image it will first be copied to the alternative boot bank, as a “last known good configuration”.
If the update should fail you could press SHIFT + R early in the boot sequence and select to boot the system from the alternative boot bank.