On Wednesday, 04/05/2006 at 11:43 ZE2, Rob van der Heij <[EMAIL PROTECTED]> wrote: > On 4/5/06, Alan Altmark <[EMAIL PROTECTED]> wrote: > > > Image backups like that won't do what you want. Linux has data in its > > internal buffer cache that needs to be written to dasd and that only > > happens when you unmount the filesystem from Linux or shut Linux down. > > There's one of the magic SysRq keys that will force Linux to synch the > disks (i.e. write out all that should have been written out). We could > probably wire that to some external rupt, but I have no idea how good > that would be. > Alternatively, provided the server does get periods of idleness, a > z/VM performance monitor could spot that moment. There's timer driven > write-out of dirty pages, and when Linux has not been writing data for > more than 30 seconds (or whatever it's set) we know it has no such > desire anymore. That might be the moment to flash the disks.
If you could sync the disks and guarantee that it won't start writing again before you complete the flash, that would be ok, but I would not wish to depend on Divine Providence to protect the consistency of the backup. However the technique of using a historical analysis to discover the "quiet times" of a server so you know that shutting it down, flashing, and restarting would have minimal impact is a good one. Alan Altmark z/VM Development IBM Endicott ---------------------------------------------------------------------- For LINUX-390 subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390
