Pursuing this just a bit further down the rabbit hole...
I can see a couple of ways this could be usefully implemented. One way would be the "no guest handshake expected" approach that just marks a guest as "Do Not Dispatch" - more or less the equivalent of pushing the STOP button on the hardware console. In a perfect world, this would be implemented as an extension to the existing CP "STOP" command -- something along the lines of "STOP CPU [addr | ALL] userid", with corresponding updates to "BEGIN" or "START" to resume execution. On the plus side, this would give a (hopefully) immediate hard stop to all virtual processors on the guest. On the downside, in-flight data that's cached at the guest level would be left dangling in mid-air, with no possibility of committing to DASD until the virtual CPU is started. Cooperative handshaking for suspension of activity might be preferable. Allowing the fantasy to run wild, a variation on "SIGNAL SHUTDOWN" - say, "SIGNAL SUSPEND" - could allow implementation of guest handshaking to cause a guest to sync file systems and enter a wait state until a later "SIGNAL RESUME" is issued externally to indicate it's time to restart the warp drive. It's all just a simple matter of programming, right? ;-) -dan. Coffin Michael C wrote:
I manage my DASD in this fashion, i.e. there are DB2 DASD groups, SFS DASD groups, Linux DASD groups, etc. etc. When running a DR backup of a group of packs we shutdown, quiesce or otherwise take steps to ensure the integrity and consistency of everything in the "group" before SnapShotting all volumes in the group. Linux is indeed a problem for all of the reasons discussed previously, particularly buffered I/O's to disk. It would be REALLY helpful if this were addressed in a future release of Linux, i.e. the ability to instruct the Linux server to flush it's buffers and write everything to disk, initiate no new applications or filesystem writes, etc. A QUIESCE and RESUME command set would be ideal. QUIESCE your Linux server prior to backup, and RESUME service once you have done everything you need to do. For Flash/SnapShot sites it would be quiesced for a matter of seconds as the DASD is snapped, but for shops without this technology the server might be QUIESCEd for hours while it's DASD is backed up to tape and RESUMEd later when it has completed. Michael Coffin, VM Systems Programmer Internal Revenue Service - Room 6527 1111 Constitution Avenue, N.W. Washington, D.C. 20224 Voice: (202) 927-4188 FAX: (202) 622-6726 [EMAIL PROTECTED]
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