I don't have a good answer to this question yet. For now I only create the heap in swap, write it to disk, and then use it as read only mmap. To ensure the writ

I don't have a good answer to this question yet. For now I only create the heap in swap, write it to disk, and then use it as read only mmap. To ensure the written file is valid, one can write it to a temporal file first, once confirmed the file is written, then mv the file to desired file name and location. This works for immutable data, but is a big blocker for me to make OPIC work on mutable back store. This problem is generally hard. See [Ensuring data reaches disk](https://lwn.net/Articles/457667/ https://lwn.net/Articles/457667/)