Hosting VOB Servers on VMware
Preventive Service Planning
Beware of System Time inaccuracies when hosting IBM Rational ClearCase VOB Servers on VMware.
Important: VMware is a supported hypervisor for hosting an Enterprise ClearCase operating system (OS) platform. Customers using VMWare as the hypervisor should strongly consider using a time daemon for management of Time within their VM environment. If customers have virtualized VOB Servers and use time stamps in their configuration specifications (config specs), they are advised to read and understand how this could affect their existing ClearCase environment. That information is provided below.
There are published issues around the inaccuracies with VMware system time management that could result in errors with the time stamping of files or metadata within a ClearCase VOB.
The main area of concern is around ClearCase environments that are dependent on time based rules used in configuration specifications (config specs). Be aware of these issues around time management as time reported to the application can actually be faster or slower than the actual time. Use of a time daemon is highly recommended to reduce the inaccuracies to less than the last time sync interval.
Refer to the VMware Information Guide Timekeeping in VMware Virtual Machines for a further understanding about the issues that arise in keeping accurate time in virtual machines.
Customers who wish to use ClearCase VOB servers in a VM environment should understand this is a vendor issue.