Sunday, October 11, 2009

OpenSolaris Performance Issues Resolved

I've been playing with some soon-to-be-released operating systems--notably Open Suse 11.2 and OpenSolaris 2010.02. I always really enjoy OpenSolaris when I run it in a virtual machine under Linux and I enjoy working on Solaris workstations at my employment. I've tried OpenSolaris on and off over the past several months on my home computers. When I've installed it directly onto a partition and run it directly on bare metal, I've noticed performance issues and I've gone back to Linux as the primary OS.

In my latest endeavors of running OpenSolaris, I noticed that the disk io seemed to be the performance killing culprit. Doing simple disk io tests under both Linux and OpenSolaris, Linux was just destroying the io numbers I was getting under OpenSolaris. My test was a simple "dd if=/dev/zero of=test bs=4048 count=100000 conv=fsync"--nothing fancy, but enough to demonstrate an issue. Linux numbers were around 60 MB/s while OpenSolaris numbers were in the 15-20 MB/s. No settings helped out the OpenSolaris numbers--dd block sizes, file system block sizes, zfs settings, etc. Interestingly enough, on an older computer, the disk io was just fine under OpenSolaris, so why was it so slow on newer/faster computer?

I was almost ready to give up and wipe the OpenSolaris partition once more, but I had one last area I had not tried. I remembered the SATA settings that are within the bios settings of my Intel motherboard. I changed the SATA mode from Legacy to AHCI. Sure enough, my OpenSolaris hard drive speeds were now on par with Linux. Inspection of the loaded modules showed that OpenSolaris had loaded the ahci driver. Additional online research shows that one should set the mode to AHCI for OpenSolaris.

I'm definitely happy with the results on all 4 home machines. 3 diverse desktop models and 1 laptop are running very smoothly. I'll plan on detailing some lessons learned and tutorials in the near future.

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