Enable Stateless Cache on Auto Deploy

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:

  1. Select the profile and right click on it
  2. Select Edit
  3. Expand System Image Cache Configuration
  4. Click on System Image Cache Profile Settings
  5. 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.

Design Constraints

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.

4 thoughts on “Enable Stateless Cache on Auto Deploy

  1. Hi, could you share what you had to do on the UCS side to get this to work? I’ve enabled flex flash but Vmware still says I don’t have a compliant stateless cache.

    1. Other than the item in the post the only other thing we had to do was create a policy to clear the SDcards and run it on the chassis. Which wipes the partition tables on the SD cards. They came with something parted and ESXi did not like it. You could also manually wipe out the part table. I hope it helps. We tested on a greenfield which made it easier. Another tech I work with blew the whole FI config to default yesterday and was able to have ESXi up to run workloads in two hours with UCS and auto deploy it was awesome.

  2. Create a scrub policy that also includes wiping your FlexFlash, select it in your service profile. We then tried just unassigning the profile so the scrub policy takes effect, but that made difference.

    We found that you need to reacknowledge the server, after that the device allows the install.

    Joseph also hit the device selection for Sydtem Image Cache to be the USB option. I don’t yet know which device is selected when you have more than one USB/SD card devices installed.

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