Sunday, September 9, 2012
In case of ESXi upgrade, ESXi implements a dual-image architecture.
Dual-Image architecture in boot disk maintains two partitions these
partitions are referred as boot banks. One boot bank will be carrying
active image of ESXi and referred to as the primary boot bank. Other
boot bank referred as alternate boot bank will be carrying the previous
ESXi image. Boot bank partition can be viewed using VI Client connected
to ESX Host.
ESXi Host -> Configuration -> Storage. From the list of
datastores select the boot disk, and then from the Datastore Details
section select properties. In ESXi 3.X boot bank partition was of 48 MB
& in case of ESXi 4.X size of boot bank partition is 250 MB.
During ESXi upgrade process the current active image will be copied to
the alternate boot bank from primary boot bank and new image will get
installed to the primary book bank. This dual-image approach helps quick
failing back to previous image in-case of any issue arise after patch
deployment or up-gradation.
To fallback to previous image, one simply need to reboot the host and
press Shift + R at the beginning of boot process to
instruct the boot loader to boot from the alternate boot bank.
After Fallback
