On Thu, 17 Apr 2008, Pascal Vandeputte wrote: > > At the moment I'm seeing read speeds of 200MB/s on a ZFS raidz > filesystem consisting of c1t0d0s3, c1t1d0 and c1t2d0 (I'm booting > from a small 700MB slice on the first sata drive; c1t0d0s3 is about > 690 "real" gigabytes large and ZFS just uses the same amount of > sectors on the other disks and leaves the rest untouched). As a > single drive should top out at about 104MB/s for sequential access > in the outer tracks, I'm very pleased with that. > > But the write speeds I'm getting are still far below my > expectations: about 20MB/s (versus 14MB/s in Windows 2003 with Intel > RAID driver). I was hoping for at least 100MB/s, maybe even more.
I don't know what you should be expecting. 20MB/s seems pretty poor but 100MB/s seems like a stretch with only three drives. > I'm a Solaris newbie (but with the intention of learning a whole > lot), so I may have overlooked something. I also don't really know > where to start looking for bottlenecks. There are a couple of things which come to mind. * Since you are using a slice on the boot drive, this causes ZFS to not enable the disk drive write cache since it does not assume to know what the filesystem on the other partition needs. As a result, writes to that disk will have more latency and since you are using raidz (which needs to write to all the drives) the extra latency will impact overall write performance. If one of the drives has slower write performance than the others, then the whole raidz will suffer. See "Storage Pools" in http://www.solarisinternals.com/wiki/index.php/ZFS_Best_Practices_Guide. * Maybe this ICH9R interface has some sort of bottleneck in its design or there is a driver performance problem. If the ICH9R is sharing resources rather than dedicating a channel for each drive, then raidz's increased write load may be overwelming it. If you are looking for really good scalable write performance, perhaps you should be using mirrors instead. In order to see if you have a slow drive, run 'iostat -x' while writing data. If the svc_t field is much higher for one drive than the others, then that drive is likely slow. Bob ====================================== Bob Friesenhahn [EMAIL PROTECTED], http://www.simplesystems.org/users/bfriesen/ GraphicsMagick Maintainer, http://www.GraphicsMagick.org/ _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
