All the running process information and state are saved to this file. You can
examine the file and you will see that it is a rather large binary file. The size of this
file will be equivalent to the memory that was being used by the domain when it was
saved. So on a reasonable Xen domain that is running some enterprise applications,
the size of this file can be very large??”in the order of a few gigabytes. Therefore, you
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must ensure that you have enough storage space where this file is saved. In this
example we saved the state to a disk file but there is no reason why you cannot save
this file to a large enough network folder or even mounted USB key. Saving the
domain to a USB key is a nifty way for you to carry your domain around in your
pocket and restore it on a different server!
A saved domain is restored by using the restore option with the xm command. This
will start up the domain again and restore it to the state the domain was in when it
was saved. There are some things you need to keep in mind when using the save and
restore feature:
The ID of the restored domain will be different from the ID the domain had
when it was saved. So when you use xm to view a restored domain, you will
notice that the ID is different.
The domain is restored to its earlier state (when it was saved) but you will
not be automatically connected to the domain's console. You will need to
explicitly run the xm command to connect to the console.
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