Re:How Mail.Ru Reduced Email Storage From 50 To 32 PB
by Jakob on Saturday January 28, 2017 @01:43PM
(#13507956)
This was answered in the comments section of the high scalability article [0]:
> Deleting email (and generally any file) is not transactional. It can be rollbacked by server poweroff, for example. This can generate additional decrement, that is the problem. Generally, 2-phase commit between "email deleter" and "counter decrement" is not enough. You will also need 2-phase commit between "deleter" and physical disk(not its cache), and so on. Also, a network error can occur between this 2 phases. We do not want to lose user's data in any case.
> Deleting email (and generally any file) is not transactional. It can be rollbacked by server poweroff, for example. This can generate additional decrement, that is the problem. Generally, 2-phase commit between "email deleter" and "counter decrement" is not enough. You will also need 2-phase commit between "deleter" and physical disk(not its cache), and so on. Also, a network error can occur between this 2 phases. We do not want to lose user's data in any case.
[0] http://highscalability.com/blog/2017/1/2/efficient-storage-h...