On Tue, Feb 22, 2011 at 2:24 PM, NeilBrown <neilb@xxxxxxx> wrote: > > > Write-through. > > However I am tempted to make it write-back as filesystems now submit 'flush' > requests which can be used to flush the cache. I wonder if you would be able > to notice any performance difference... I imagine it would depend on your file system and what you are doing with it. In my application, I am typically generating multi-gigabyte files, with linear writes, at a reasonably fast pace. So write-back might help. On the other hand, "flush" alone might not be sufficient for high performance. I do not know much about Linux file system internals, but it seems to me that there are two separate but related concepts. One is ordering of operations (to ensure file system consistency). The other is flushing (for data integrity; i.e. fsync()). If the file system actually has to flush to ensure consistency -- rather than just tagging its writes with ordering constraints -- I think you might lose a lot of your performance to all of that flushing. But since I really do not know what the kernel provides internally in this regard I will stop rambling now. - Pat -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
