Are you using a USB or SD media as a boot device for ESXi? This is a great solution, but there are a few things that you may not be aware of.
We use this configuration on all our ESXi hosts. All was working well for about 1 year, until I saw the following error on one of our VMWare hosts:
"Lost connectivity to the device mpx.vmhba32:C0:T0:L0 backing the boot filesystem /vmfs/devices/disks/mpx.vmhba32:C0:T0:L0. As a result, host configuration changes will not be saved to persistent storage."
As it turns out my trusty 2GB usb pin drive that I thought was reliable, turns out it really is not reliable because there are differences in Flash Chip types. ESXi will write to the USB
There are 3 different types of flash chip types: 1) TLC 2) MLC 3) SLC
For a USB boot device (or SD boot device) you want to use SLC, Single Layer Cell. SLC is the most durable, reliable and is the highest performance out of the 3 types.
SLC- Single Layer Cell
• High performance
• Lower power consumption
• Faster write speeds
• 100,000 program/erase cycles per cell
• Higher cost
• A good fit for industrial grade devices, embedded systems, critical applications.
MLC- Multi Layer Cell
• Lower endurance limit than SLC
• 10,000 program/erase cycles per cell
• Lower cost
• A good fit for consumer products. Not suggested for applications which require frequent update of data.
TLC- Three Layer Cell
• Higher density
• Lower endurance limit than MLC and SLC
• TLC has slower read and write speeds than conventional MLC
• 5,000 program/erase cycles per cell
• Best price point
• A good fit for low-end basic products. Not suggested for critical or important applications at this time which require frequent updating of data.
(From Centon Electronics website)
Full article: Chiptype - Centon Electronics, Inc.
Here are a couple of guidelines for using USB to boot ESXi:
- Buy SLC media.
- Make sure you have a couple of copies of you ESXi USB's available. (especially if you are using the cheap TLC variety)
- Create a persistent scratch area on a SAN LUN (if not changed you will loose logs if you need reboot the host) KB1033696
- If your using a USB to boot ESXi, never remove the boot USB from a running ESXi server. (Yes really - I found a few articles about how to resolve this interestingly enough - see: ESXi and USB failure? | Adventures in a Virtual World )
Good luck!
KB articles regarding USB/flash:
Installing ESXi 5.x on a supported USB flash drive or SD flash card (2004784)
Lost or degraded connectivity to storage device (1009553)