Is it possible to install and run Parallels Cloud Server from an SD card?
This setup has never be tested, however the behavior should be the same as RHEL 6 and CentOS 6 - PCS will install successfully if the mentioned systems can be installed successfully.
You should also consider these points:
It is necessary to make sure that boot from SD card is possible at all.
SD card should be class 10 and 12 GB size.
Any SD card is slower then a hard drive which will influence the performance.
If you intend to run the server without swap, make sure there is no memory overselling (especially on the servers which act as MDS or CS when PCS is part of Parallels Cloud Storage). Putting swap on SD card is not recommended as well due to lower speed and limited number of rewrite cycles.