Better than POSIX?
Posted Mar 17, 2009 15:42 UTC (Tue) by quotemstr
Parent article: Better than POSIX?
Thank you for a balanced discussion of one of the most inflammatory technical (as opposed to legal or social) issues in recent memory. The "worse is better" approach is not unique to unixland, and in the days of small computers with limited resources, counting on applications to not do silly things made sense.
But I firmly believe that today the kernel can provide a great deal of additional robustness at practically no performance cost. An "ordered rename" is a no-brainer. Not only do existing applications suddenly do the right thing, but also an "ordered rename" allows application developers to inform the kernel of constraints that are simply impossible to express when applications are required to
fsync before every useful
Some people say that a non-ordered
rename gives the kernel more freedom to optimize. That view is a red herring: with a non-ordered
rename, applications must
fsync before the rename to have sensible semantics. So really, the choice isn't between an ordered and a non-ordered
rename, but between
ordered_rename; the latter actually gives the kernel greater latitude in optimizing IO.
rename be either neutral or beneficial in every real-world situation. Here's my challenge to anyone reading this: come up with a non-contrived scenario in which an ordered rename (i.e., an implicit write barrier) would be harmful.
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