However, it would appear that the version of mdadm in shipping versions of Ubuntu (at least - maybe other distros too) doesn't support the Smart Response Technology (SRT - http://www.intel.com/content/www/us/en/architecture-and-technology/smart-response-technology.html ) feature that's a part of RST and is used by Lenovo to build a hybrid one-stripe RAID0 device from the HDD with a cache on the SSD (I'm sure Lenovo have a good reason for not using a SSHD). Dan Williams of Intel submitted a series of patches to mdadm to support SRT back in April 2014: https://marc.info/?l=linux-raid&r=1&b=201404&w=2 . Perhaps now there's shipping hardware that requires them, there'll be the impetus for distro vendors to get them integrated into mdadm, and their auto-detection in their installers to use the functionality provided sanely.
Storm in a teacup
Such patches are unnecessary, as mdadm already supports Intel Rapid Storage Technology (RST - http://www.intel.co.uk/content/www/uk/en/architecture-and-technology/rapid-storage-technology.html ) for simple RAID (e.g. levels 0, 1, 10) arrays, allowing them to be assembled as md or dmraid devices under Linux.
However, it would appear that the version of mdadm in shipping versions of Ubuntu (at least - maybe other distros too) doesn't support the Smart Response Technology (SRT - http://www.intel.com/content/www/us/en/architecture-and-technology/smart-response-technology.html ) feature that's a part of RST and is used by Lenovo to build a hybrid one-stripe RAID0 device from the HDD with a cache on the SSD (I'm sure Lenovo have a good reason for not using a SSHD). Dan Williams of Intel submitted a series of patches to mdadm to support SRT back in April 2014: https://marc.info/?l=linux-raid&r=1&b=201404&w=2 . Perhaps now there's shipping hardware that requires them, there'll be the impetus for distro vendors to get them integrated into mdadm, and their auto-detection in their installers to use the functionality provided sanely.