Jochen Schulz wrote:
Simon:Jacob S wrote: # hdparm /dev/hde [...] # hdparm /dev/hdgAgain, I think you are searching in the wrong direction. Your 'hdparm -tT' results clearly showed that the great difference between your servers doesn't lie in hard disk performance (48 to 43 MB/s), but in Memory/CPU performance (278 to 58 MB/s).
That would be a very gross misconfiguration. To me it seems far more likely that raid caching is simply disabled, possibly in the driver. (Grasping straws here, but maybe the card was blacklisted for not obeying the fsync() function, and therefore deemed unsafe for atomic commits whenever write caching is enabled, just as one possible reason, however unlikely. See Slashdot discussion on "Your hard drive lies to you": http://hardware.slashdot.org/article.pl?sid=05/05/13/0529252&tid=198&tid=128 ) When doing the same SQL query
several times the hard disk shouldn't be bothered much anyway since either MySQL or a´t least Linux itself should have cached the data. J.