We use the Raspberry Pi Compute Module, i.e. a special, stripped-down version of the Raspberry Pi which fits on a 200 pin SO-DIMM module. This version does not

We use the Raspberry Pi Compute Module, i.e. a special, stripped-down version of the Raspberry Pi which fits on a 200 pin SO-DIMM module. This version does not use an SD card but has a 4 GByte eMMC on-board. (It would be possible to use an SD card in addition to the eMMC but we don't make use of that.) Of course the eMMC is still based on flash, which has a limited lifetime. So we use a customized version of Raspbian which has swap disabled by default (can be enabled if you need it) and tunes the syslog configuration to reduce the amount of log data written. It's also possible to use a tmpfs-backed /var/log (can be enabled with a mouse click or a simple command). That way we try to prolong the lifetime of the eMMC as much as possible. We've also been in talks with the Foundation about this and they have asserted that the eMMC is of good quality and should last for the typical lifetime of a PLC (which can be decades).