Tux3: the other next-generation filesystem

For RAIDs, there should be few selectable options:
- read (all mirrors) after writes, report error if content differ (slow)
- write (all mirrors) and return if all writes successfull, post a read of the same data and report delayed error if content differ.
- write (one mirror) and return as soon as possible, post writes to other mirrors, then post a read of the same data (all mirrors) and report delayed error if content differ.
Obviously, for previous test, you should run the disks with their cache disabled.

Those can run with cache enabled:
- read all mirrors and compare content, report error to the read operation if content differ (slow)
- read and return first available data, but keep data and compare when other mirrors deliver data; report delayed error if mirrors have different data.

That is better handled in the controller hardware itself, I do not know if some hardware RAID controller do it correctly.
I am not sure there is a defined clean way to report "delayed errors" in either SCSI or SATA, there isn't any in ATA interface (so booting from those RAID drives using the BIOS may be difficult).
Moreover the "check data" (i.e. read and compare) in SCSI is sometimes simply ignored by devices, so that may have to be implemented by reads in the controller itself.
I am not sure a lot of users would accept the delay penalties due to the amount of data transferred in between controller and RAID disks...