> > Anyhow, in the case of DBs, ARC indeed becomes a vestigial organ. I'm > surprised that this is being met with skepticism considering that > Oracle highly recommends direct IO be used, and, IIRC, Oracle > performance was the main motivation to adding DIO to UFS back in > Solaris 2.6. This isn't a problem with ZFS or any specific fs per se, > it's the buffer caching they all employ. So I'm a big fan of seeing > 6429855 come to fruition.
The point is that directI/O typically means two things: 1) concurrent I/O 2) no caching at the file system Most file systems (ufs, vxfs, etc.) don't do 1) or 2) without turning on "directI/O". ZFS *does* 1. It doesn't do 2 (currently). That is what we're trying to discuss here. Where does the win come from with "directI/O"? Is it 1), 2), or some combination? If its a combination, what's the percentage of each towards the win? We need to tease 1) and 2) apart to have a full understanding. I'm not against adding 2) to ZFS but want more information. I suppose i'll just prototype it and find out for myself. eric _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
