Quoth Darren J Moffat on Thu, Aug 09, 2007 at 10:32:02AM +0100: > Prompted by a recent /. article on atime vs realtime ranting by some > Linux kernel hackers (Linus included) I went back and looked at the > mount_ufs(1M) man page because I was sure that OpenSolaris had more than > just atime,noatime. Yep sure enough UFS has dfratime. > > So that got me wondering does ZFS need dfratime or is it just not a > problem because ZFS works in a different way.
I believe ZFS will delay atime updates waiting for more writes to come in, but it will eventually write them anyway (5 seconds?). dfratime postpones the write until another write comes in, so it seems legitimate to me for ZFS to have such an option. > If ZFS did have dfratime > how would it impact the "always consistent on disk" requirement. One > though was that the ZIL would need to be used to ensure that the writes > got to disk eventually, but then that would mean we were still writing > just to the ZIL instead of the dataset itself. I don't think dfratime changes the disk consistency at all. Wouldn't writing to the ZIL with dfratime on defeat the purpose? If we need to write to the ZIL for some other write, though, then it would be ok to flush the atime updates out too. All that said, I believe the primary use case for dfratime is laptops, and therefore it shouldn't be a high priority for the ZFS team. David _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
