On Mon, 2016-08-01 at 11:14 +1200, Jim Cheetham wrote: > On Sun, Jul 31, 2016 at 12:21 PM, Adrian <[email protected]> wrote: > > > > What is the best way to mirror an Ubuntu server that runs several > > VMs > > to an identical hardware configuration for the purpose of having a > > stand-by warm swap server. > Obviously there is no single approach that is "the best way". > > Instead, what you will end up with will be lots of different > techniques with differing costs/complexities, offering different > benefits :-) Many of them will say "if you were doing things > differently from the beginning ..." - consider these, the cost of > reworking your environment to fit the answer might be better than > trying to retrofit availability into your current environment ... > > But, I guess it's reasonable to look for the approach that has the > least change from your current working practices, so you don't have > to > change too much at one go and therefore lose understanding of how the > system actually works. > > Step Zero: Backups of everything are essential - remember that "a > backup is not a backup unless you can restore, so test restore every > time you backup". If you can restore from backup quickly enough, you > might already have your near-real-time spare. > > Question One: How will you switch between the two? What IP addresses > will they have, when? If you change the IP of one machine to the > "primary" address, will your local network switch realise you've > changed MAC address? Or will you change that too? (If you do change > IP > address, how will you know that you're logged in to the correct > server > - especially important while they are both working). Will you change > the primary status using the local firewall/router? > > If your machines are on the same LAN, you might approach the problem > by making the two machines identical in real-time, perhaps by using > disk-level clustering; DRDB is a great approach for this, very > mature. > If all the user data (i.e. the VMs, etc) are on the shared volume, > either machine will get the same view. If the two machines have the > same OS-level configuration, either can do the job of running the VM > - > but you're going to need to make sure that they don't both attempt to > do so at the same time. > > That's a start - does that help? > > -jim > _______________________________________________ > Linux-users mailing list > [email protected] > http://lists.canterbury.ac.nz/mailman/listinfo/linux-users >
Yes, it does help. A lot. Thanks. I was afraid of that, that there is no best way. The background of this is that this is a new production server and both it and the mirror will be in the same LAN behind a firewall, both with private IP addresses. Hardware-wise they will be cvasi-identical - same motherboard, same disk controllers, same disks, same RAM, same RAM type, same networks interfaces, but there may be some small differences I am not aware of at this time. They will both run Ubuntu server 16.04 with the same number and types of VMs A couple of hours downtime in case of failure is acceptable so the switch between them can even be done manually by changing the settings in the firewall, but most likely I will automate the switch and set an alarm or notification for the event. There is another redundancy layer, but that's a subject for another thread maybe. Backups will be performed both locally and remotely and be integrated in the current backup policy. Restoring backups might work, with full backup/restore in weekend followed by incrementals every weekday. However, the data has the potential to grow rapidly and probably in a year or so this technique will have to be replaced by something else. DRBD looks cool. I will have to re-think partitions, but that's achievable. If I may deviate a bit from the initial subject, suppose I go down the path with different techniques employing rsync, database replication and others, is there a project/package/application that will allow me to chain various scripts, pass parameters and create other logic and then show the end result in a (preferably) web interface? I'm thinking something similar to the old Opalis that eventually got bought by MS in 2009. Or a way that will make my life and that of whomever will take over later on easier in maintaining the resulting scripting tangle. Adrian _______________________________________________ Linux-users mailing list [email protected] http://lists.canterbury.ac.nz/mailman/listinfo/linux-users
