Atomicity vs durability
Posted Mar 15, 2009 12:48 UTC (Sun) by man_ls
In reply to: Atomicity vs durability
Parent article: Ts'o: Delayed allocation and the zero-length file problem
Exactly. What is missing now is atomicity in the face of a crash. To quote myself from a few posts above:
"Atomic without a crash" is not good enough; "atomic" means that a transaction is committed or not, no matter at what point we are -- even after a crash.
Durability (what fsync provides) is not needed here; durability means that the transaction is safely stored to disk. What we people are requesting from ext4 is that the property of atomicity be preserved even after a crash.
Even if the POSIX standard does not speak about system crashes it is good engineering to take them into account IMHO.
to post comments)