I haven't heard about CIO for Linux so I guess they don't have it. ...PolyServe direct I/O is free of write-ordering locks and mtime/atime updates as is ODM and Quick I/O on Veritas SFRAC. I/O on these are fully concurrent, we just down say CIO, because DIO that is not CIO is not really DIO...the CIO guys lagged in the critical deliverable so when they finally produced it they had to make it sound like it was something novel. That is, anythnig called DIO that is not also inherently CIO is just a partial implementation. After all, we aren't talking about splitting atoms. Oracle 6.0.26 on Sequent Dynix/ptx supported async/direct I/O on ufs and it was fully concurrent...in 1991. -- //www.freelists.org/webpage/oracle-l