What sort of disk is VMware ESXi running on?

#Edit 5th Jan, 2012#
OMG – Don’t read all this crap, I’ve stumbled on how to actually do this properly. Just run this:

~ # esxcfg-info -e
boot type: visor-usb


#Original Post#
We’re working on a boot from SAN ‘modernization’ project at the moment. Which is another way to say we’re getting rid of it. It’s way too complicated! And if the SAN goes down, all the boot partitions go with it. This just introduces an extra dependency that can completely nullify any fault tolerant or HA strategies that you may have in place in the vSphere layer. No prizes for guessing who this has happened to recently!

What to do instead? The new HS22V blade systems we are using have a tiny little usb port on the motherboard where you can install a USB key. Load ESXi on it, and you’re golden.

The key

So I need to make a list of which hosts need fixing up and which are booting from usb already or are using local storage. We’d started this process recently but want to step it up now. But which ESXi machines in the farm are booting from what ? How can you tell?

With fdisk of course – simply enable Remote Tech Support mode (see here for details) and ssh into your host.


fdisk -l

and look for the ‘*’ in the boot column. That’s the partition that ESXi is booting from. If you see a device called /dev/disks/mpx.vmhba32:C0:T0:L0 , you’re booting from usb. If the device is something more like /dev/disks/naa.600508e000000000194a56b4310b4804 you are booting from SAN or a local disk.

Here’s the fdisk output for my usb stick.

Disk /dev/disks/mpx.vmhba32:C0:T0:L0: 2038 MB, 2038431744 bytes
64 heads, 32 sectors/track, 1944 cylinders
Units = cylinders of 2048 * 512 = 1048576 bytes

                           Device Boot      Start         End      Blocks  Id System
/dev/disks/mpx.vmhba32:C0:T0:L0p1             5       900    917504    5  Extended
/dev/disks/mpx.vmhba32:C0:T0:L0p4   *         1         4      4080    4  FAT16 <32M
/dev/disks/mpx.vmhba32:C0:T0:L0p5             5       254    255984    6  FAT16
/dev/disks/mpx.vmhba32:C0:T0:L0p6           255       504    255984    6  FAT16
/dev/disks/mpx.vmhba32:C0:T0:L0p7           505       614    112624   fc  VMKcore
/dev/disks/mpx.vmhba32:C0:T0:L0p8           615       900    292848    6  FAT16
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