Auto Deploy Really?
Yes a big autodeploy post is going to be following up soon. I can really seen the benefit of auto deploy in larger environments. I’ll be posting the architectural recommendations and failure scenarios soon. Today I am posting about stateless cache and USB.
What is stateless cache and why do I care?
Stateless cache allows your auto deployed ESXi host (TFTP image running in memory) to be installed on a local hard drive. This enables you to boot the last running configuration without the presence of the TFTP server. It’s a really good protection method. It is enabled by editing the host profile and in 5.5 it can be enabled using the fat client:
- Select the profile and right click on it
- Select Edit
- Expand System Image Cache Configuration
- Click on System Image Cache Profile Settings
- Select the drop down and choose the stateless caching mode you want.
This all sounds great but we had a heck of a time trying to get it to stateless cache to SD cards on our UCS gear. A coworker discovered that SDcards are seen as USB devices. Once we select “Enable stateless caching to a USB disk on the host” everything worked.
Using stateless caching will protect you against a failure of TFTP and even vCenter but DHCP and DNS are both still required for the following reasons:
- DHCP to get IP address information
- DNS to get hostname of ESXi host
Stateless does not remove all dependencies but it does allow quick provisioning.