Does Linux tmpfs filesystem need the sync option?
I had to search a bit. According to
man mount
The sync option is relevant only for a limited number of filesystems, not for tmpfs.
So the answer is: It does not matter, since it is ignored by tmpfs.
Sync makes the data beeing dumped onto the disk without beeing saved in cache
"Standard" Linux manual states:
sync All I/O to the filesystem should be done synchronously.
In the case of media with a limited number of write cycles
(e.g. some flash drives), sync may cause life-cycle shortening.
So it's not about cacheing but rather about durability. Writing synchronously doesn't mean there wouldn't be caching (for e. g., writethrough is well-known caching approach which is very different to writeback but both still are cacheing).
In my option it would be odd if a ramdisk would be cached in RAM.
As explained it doesn't prohibit cacheing but rather prohibits writeback-like behaviour. What would be odd is "durability" for RAM disk though.