Monday, August 1, 2016

VSAN - cache disk unavailable when creating disk group on Dell

I ran into an issue at customer where the SSD which is to be used as the cache disk on the VSAN disk group was showing up as regular HDD.  However when I reviewed the storage device the disk is visible and is marked as flash...weird.  So what is going on here.

As I found out this due to a flash device being used with a controller that does not support JBOD.

To fix this I had to create a RAID 0 virtual disk for the SSD.  If you have a Dell controller this means you have to set the mode to RAID but make sure that all your regular HDDs to be used in the disk group is set to non-raid!  Once host is back online you have to go and mark the SSD drive as flash.  This is the little "F" icon in the disk devices.

This environment was configured with all the necessary VSAN prerequisites for Dell in place, you can review this on the following blog post:
http://virtualrealization.blogspot.com/2016/07/vsan-and-dell-poweredge-servers.html


Steps to setup RAID-0 on SSD through lifecycle controller:


  1. Lifecycle Controller
  2. System Setup
  3. Advanced hardware configuration
  4. device settings
  5. Select controller (PERC)
  6. Physical disk management
  7. Select SSD
  8. From drop down select “convert to Raid capable”
  9. Go back to home screen
  10. Select hardware configuration
  11. Configuration wizard
  12. Select RAID configuration
  13. Select controller
  14. Select Disk to convert from HBA to RAID (if required)
  15. Select RAID-0
  16. Select Physical disks (SSD in this case)
  17. Select Disk attribute and name Virtual Disk.
  18. Finish
  19. Reboot

After ESXi host is online again then you have to change the Disk to flash. This is due to RAID abstracting away most of the physical device characteristics and the media type as well.

  • Select ESXi host 
  • Manage -> Storage -> Storage adapters
  • Select vmhba0 from PERC controller
  • Select the SSD disk
  • Click on the "F" icon above.