On 5 July 2012 04:26, John A. Wallace <[email protected]> wrote: > ... does the space > required for a snapshot count against the guest's allocated space designated > when the VM for this guest had been initially configured?
No, host disk space used by the snapshots is unrelated to the size of the virtual disk that the guest sees. At all times the guest sees a (virtual) disk of the configured size. Remember, the files you see are not the snapshot, they are differencing image files used as an internal mechanism to implement the snapshot. The size of the snapshot differencing image files depends on how many changes have been made since the snapshot was taken and is not directly related to the allocated size of the cirtual disk. The snapshot differencing image file could in theory grow to be as large as the virtual disk size, if many or all sectors on the virtual disk were changed (for example, if the virtual disk was securely erased inside the VM, all disk sectors would be changed and the image file would grow as large and slightly larger than the virtual disk maximum allocated size). It is probably best to think of the snapshot differencing image files as a just the internal mechanism that VirtualBox uses to implement snapshots. Exactly how that internal mechanism works can be interesting, but in most cases you don't need to know how it works. One exception is this: When deleting snapshots, make sure you have plenty of free space on the host drives (I recommend at least as much free space as the total size of disks allocated to the VM). When a snapshot is deleted, the changes stored in the corresponding differencing image file are merged into another differencing image file (or with the main VDI file when the topmost snapshot is deleted). This (usually) causes that other file to grow in size as changes are merged into it, and more host disk space is used. When the merge is finished, the source corresponding differencing image file is deleted. If the host were to run out of disk space during the merge, it wouldn't be good! -- Mark ------------------------------------------------------------------------------ Live Security Virtual Conference Exclusive live event will cover all the ways today's security and threat landscape has changed and how IT managers can respond. Discussions will include endpoint security, mobile security and the latest in malware threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ _______________________________________________ VBox-users-community mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/vbox-users-community _______________________________________________ Unsubscribe: mailto:[email protected]?subject=unsubscribe
