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    |   xen-users
Re: [Xen-users] A simple backup 
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Mark Williamson wrote:
 When you take an atomic snapshot of a domU's state, it's much the same kind of 
backup image as you'd get by yanking the power from a server, removing its 
hard drive and copying it byte-for-byte - often readable but definitely not 
clean.  That consistency problem is what makes it impossible to guarantee 
that such backups are definitely readable.
  
 
Hi Mark,
Some thoughts about your comment.
In our environment, one of the requirements for the OS and applications 
is that it must be able to recover quickly and cleanly from a power 
failure. This is actually one of the reasons why we're starting to 
migrate some stuff to zfs : because, when used properly, it always 
guarantee filesystem consistency in the event of power failure. 
IMHO, even the best commercial SAN-based backup solution uses that 
assumption, so for practical purposes, atomic backup for domU's storage 
should be sufficient. 
 It would be nicer if you could somehow guarantee a 
consistent filesystem state on your disk snapshot.  I've been looking into 
how to do this and I believe it's quite possible to modify the code to 
support this properly.
 
It would be interesting if you can make it happen.
Regards,
Fajar
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