Feizhou wrote: > There are two levels of caching. Hardware and software. Hardware level > caching involves in your case the 3ware card cache and the individual > disk caches. > > Software level involves the kernel's disk cache. > > There are FS level settings available. You can mount the filesystem with > the sync option which means writes are to be done synchronously and so > these are not stored in the kernel's cache. There is also dirsync which > can to used to ensure metadata on files/directories are also written > synchronously. > > You can also do it on a per file level by setting the file's sync (S) > attribute. > > So a completely paranoid setup would include making sure that the > file/filesystem is sync'ed and also turning off the write cache on the > hardware. You should be able to set sync at the software level and leave > the hardware write caching on and see a difference. So what do *you* do when you disable write caching on one of your systems?