To reply to my own message.... this article offers lots of insight into why dd access directly through raw disk is fast, while accessing a file through the file system may be slow.
http://www.informit.com/articles/printerfriendly.asp?p=606585&rl=1 So, I guess what I'm wondering now is, does it happen to everyone that ZFS is under half the speed of raw disk access? What speeds are other people getting trying to dd a file through zfs file system? Something like dd if=/pool/mount/file of=/dev/null bs=128k (assuming you are using default ZFS block size) how does that compare to: dd if=/dev/dsk/diskinzpool of=/dev/null bs=128k count=10000 If you could please post your MB/s and show output of zpool status so we can see your disk configuration I would appreciate it. Please use file that is 100MB or more - result is be too random with small files. Also make sure zfs is not caching the file already! What I am seeing is that ZFS performance for sequential access is about 45% of raw disk access, while UFS (as well as ext3 on Linux) is around 70%. For workload consisting mostly of reading large files sequentially, it would seem then that ZFS is the wrong tool performance-wise. But, it could be just my setup, so I would appreciate more data points. This message posted from opensolaris.org _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
