Hi. I''m benchmarking xen 3 and xen 4 to see which one to chose for my vm that need to be windows 2008 r2 x64 to run sql server 2008 r2. I''m using 2 disks same brand and model, Centos 5.8 x64 no RAID. After some test Xen 3 stock had give to me better numbers, but this message is not about this yet, what took my attention was the results sqlio give to me. Maybe some of u had use this tool to benchmark disk for sql server, the machine is a AMD FX 6100 6 cores 3.3GHZ. Dom-O have 2 cores 1GB RAM Dom-U have 4 cores 8GB RAM In both installations. This took my attention: Xen 3 sqlio output: using system counter for latency timings, 103127539 counts per second Now Xen 4.1 sqlio output: using system counter for latency timings, 3579545 counts per second I had ask at sql server forum and no one have answer me the meaning of this line, counts per second. This is related to Xen, I will try 3.4 and see my numbers, but I still don''t know the meaning and why I got different numbers in this line if I''m using the same HW and same settings. Thanks!!! NOTE: Once I finish my benchmark I will return here, I must finish this week.