Have been testing white box system with SuperMicro X8DTL motherboard with various SATA hard disks such as 7,200RPM Seagate Constellation ES and 10,000 RPM Western Digital VelociRaptor.
Have tested Fedora 15, Fedora 16, Ubuntu 11, running SysBench with the command found here MySQL High Performance blog
Disk write results are abysmal - typically results such as:
Operations performed: 0 Read, 3635 Write, 3635 Other = 7270 Total Read 0b Written 14.199Mb Total transferred 14.199Mb (145.39Kb/sec) 36.35 Requests/sec executed
On the other hand, a tier1 server with exactly the same CPU and 7,200RPM SATA hard disks running Fedora 15 produces these test results:
Operations performed: 0 Read, 151453 Write, 151453 Other = 302906 Total Read 0b Written 591.61Mb Total transferred 591.61Mb (5.9159Mb/sec) 1514.48 Requests/sec executed
I cannot understand how there can be such a massive difference and that the SuperMicro based system is producing such awful disk write performance.
I have tested various things including tweaks to fstab, scheduling, disabling disk standby and using sar, iostat, vmstat and so on to look for potential problems. But
%iowait and so on don't show anything unusual. Also
vm.zone_reclaim_mode as indicated here Poor disk performance although default setting on Fedora is already 0.
I tried different BIOS settings for the hard disk including IDE and AHCI. Would expect that AHCI should be the best, but write performance difference between IDE and AHCI options is negligible.
Anyone have ideas?