An update : I've moved all the VM memory files into a tmpfs. Confirmed with lsof that the mm0 and ram0 files are on that tmpfs. Though not the WinXP's mm0... After 2 days, back to the same problem. What's more iostats -tkx 10 shows %util nearly maxing out every 30 seconds. Running top at the same time, the top processes are vmware-vmx, but it varies amoung which VM so I can't accuse a single instance. Here is iostat output from with no user logged in : http://awale.qc.ca/vmware/iostat.20090927.2 This is iostat after 2 days of all VMs working : http://awale.qc.ca/vmware/iostat.20090930.1 Next up, downgrading to CentOS 4. Which is going to be annoying, for a variaty of non-techncal reasons. -Philip