On Sun, 14 Feb 2010, Dave Pooser wrote:
c7, c8 and c9 are LSI controllers using the MPT driver. The motherboard has 6 SATA ports which are presented as two controllers (presumably c10 and c11) one for ports 0-3 and one for ports 4 and 5; both currently use the PCI-IDE drivers.
One should expect that the IDE interface will be less performant than the SATA interface. For example, it seems likely that IDE does not support NCQ, so only one write could be scheduled at a time while SATA can burst multiple writes into the drive cache at a time. This would explain if the IDE drives seem to be 100% busy while the SATA drives are almost idle. This would cause issues for synchronous writes. Absent careful engineering, raidz2 usually only has one bottleneck at a time.
See "http://en.wikipedia.org/wiki/Integrated_Drive_Electronics#IDE_and_ATA-1";.
That said, I think that this is probably *a* tuning problem but not *the* tuning problem, since I was getting acceptable performance over CIFS and miserable performance over FC. Richard Elling suggested I try the latest dev release to see if I'm encountering a bug that forces synchronous writes, so
A difference in the way synchronous writes are handled could certainly make a huge difference.
It is useful to do asynchronous and synchronous write benchmarks on the local system before getting the higher level protocols involved.
As far as the warning about different sized devices goes, I am wondering if there is a limit to the maximum size of an IDE-based device and so some devices are claimed larger than others.
Bob -- Bob Friesenhahn bfrie...@simple.dallas.tx.us, 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
