Snapshot of my current (June, 2012) thinking on how Fermi might make use of VMs to freeze on a particular OS, presumably rhel6.
Scope
What activities will take place inside VMs? Here is a provisional list:
- Interactive code development, testing and debugging
- SCons release manager
- sys tests
- MC production
- Reprocessing
Depending on exactly when rhel6 becomes deprecated, the following might also have to run in VMs (but I hope not):
- L1 processing
- Online monitoring
- ASP
Resources
What resources do the above activities require? Which activities require which resources? The following table addresses these questions.
Activity\Resource |
RM db (MySQL) |
Calib db (MySQL) |
Moot db (MySQL) |
Calibrations (archive) |
Moot configs (archive) |
CVS |
RM builds |
Batch system |
|---|---|---|---|---|---|---|---|---|
Code devel |
no |
yes |
yes |
yes (or copy) |
yes (or copy) |
yes |
yes |
would be nice |
RM |
yes |
yes (for running test programs) |
yes |
yes |
yes |
yes |
yes |
yes |
Sys tests |
no |
yes |
yes |
yes |
yes |
no |
yes |
yes |
MC prod |
no |
yes |
yes |
yes |
yes |
no |
yes |
yes |
Reprocessing |
no |
yes |
yes |
yes |
yes |
no |
yes |
yes |
Note "batch system" should be interpreted loosely. It might be the centrally-supported batch system (lsf or its descendent); it might be something specialized for use from VMs.
Where
..are the various activities run? Where do the resources reside? Assuming all the activities occur inside VMs there are at least three possibilities:
- Activity is available from an "appliance": pre-configured VM. Must be used in a machine that can act as "host"; that is, has VirtualBox or similar software installed. For more about how this works, see Tom's page on a ScienceTools appliance
. - Activity is available in a VM which is normally already up and running (e.g., with SLAC-maintained machine as host)
- Activity is available in a transient VM: VM exists which has been configured to support the activity, but it may not be up and running. A "start VM" step is required before using it.
..are the resources such as MySQL, CVS located? There are two plausible places:
- SLAC centrally-maintained server (where they are now)
- Stable VM running within a SLAC centrally-maintained host.
1. will most likely be preferable so that we won't have the burden of maintaining them and so that the databases may be easily read, e.g. by the server for SCons RM web pages. It seems likely but not certain that CVS and MySQL will continue to be supported by centrally-maintained machines by the end of Fermi's lifetime. If not, we'll have to go with 2.
File systems such as the calibration archive, moot archive and RM builds which VM-sequestered processes can write to will need some special handling.