Re: [Xen-users] Xen 4.0 feature request

[John Haxby <john.haxby@xxxxxxxxxx>]

On 07/07/09 16:38, Enrico Valsecchi wrote:
> During my message in this thread, I have write that vmware
> have a very powerfull tool that allow to try a consistent snapshot....
> ....I does not have idea that this tool work, but....
> ...it work!
> And it's make vmware very powerfull, with a really and simple backup
> possibility,
> regardless environment....
>
>    
Xen's snapshot method is no less good than vmware's, it's just 
different.  For VMware workstation you can have a nice gui where you 
have a snapshot and you can see hierarchies of snapshots and it's all 
really nice.  For xen you have to do this "by hand" on the command line, 
but it's no less flexible.  You could write a fancy gui to keep track of 
your snapshots though.
You could argue that a VMware snapshot is much more flexible because it 
doesn't require a complete copy of the disk and the memory of the 
running guest to be stored.   Well, if you use one of the numerous 
copy-on-write mechanisms (qcow, lvm, zfs, btrfs, reflink, probably 
others) you can do the same, but xen doesn't need to implement that for you.
And then you've got the problem of getting the guest into a consistent 
shape for the snapshot because that's how you do backups.  VMware seems 
to tout this quite a lot, but what's not mentioned is that is requires 
cooperation from the guest and the applications running in it.  This is 
no different from vmware.
VMware has nice point and shoot (or point and click) mechanisms for 
taking snapshots and that makes it look really nice and powerful.  When 
you get down to the nitty gritty, though, it doesn't have anything that 
xen doesn't.   All that VMware has is the point and click UI ...
jch

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