On 11/03/2017 09:02 AM, hw wrote:
Robert Nichols wrote:
How would you recover if that server were suddenly destroyed, let's say by a
power supply failure that fried the motherboard and all the disks? If you can't
bring up a machine on new, bare iron starting with nothing but your backups and
a CD or USB stick with a recovery tool, you need to seriously reconsider your
backup strategy.
That´s a very good point.
What options are there to make complete and consistent backups of machines
and VMs while they are running? Just shutting down a VM to make a backup
is troublesome because you sometimes need to run 'virsh shutdown xx' several
times for the VM to actually shut down, and I have VMs that do not shut down
no matter how often you try. If you manage to shut down the VM, there is no
guarantee that it will actually restart when you try --- and that goes for
non-VMs as well. Shutting them down manually frequently to make backups is
not an option, either.
Every backup tool that can be run on a physical machine can also be run in the
VM. For databases that cannot be simply copied while they are active, there
should be a way to generate a snapshot or other consistent representation that
can be backed up and restored if necessary, and any database that does not
provide such a capability should not be considered suitable for the task at
hand. Long-running jobs should always have checkpoints to allow them to be
continued should the machine crash. (I have such a job running right now.
Coincidentally, it's verifying the consistency of 3 years of backups that I
just reorganized.)
There is no "one size fits all" answer. The needs of a transaction processing
system that can never, ever lose a transaction once it's been acknowledged are radically
different from those of a system that can afford to lose an hours, or days, worth of work.
--
Bob Nichols "NOSPAM" is really part of my email address.
Do NOT delete it.
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