Opened 6 years ago
Last modified 5 years ago
#17461 new defect
writethrough affected by snapshots
| Reported by: | Loafer | Owned by: | |
|---|---|---|---|
| Component: | virtual disk | Version: | VirtualBox 5.2.4 |
| Keywords: | Cc: | ||
| Guest type: | Windows | Host type: | Windows |
Description
I made this critical because not everyone will check for correct functionality. Restoring a snapshot will cause an unexpected data loss on a drive of type writethrough.
I've got a VM with a main drive and an attached writethrough drive. I see twice as many .vdi files than .sav files in the snapshot directory. And yes a restore changes the writethrough drive.
C:\Program Files\VirtualBox>VBoxManage showmediuminfo disk e:\dataw10.vdi
UUID: xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Parent UUID: base
State: created
Type: writethrough
Location: E:\DataW10.vdi
Storage format: VDI Format
variant: fixed default
Capacity: 4096 MBytes
Size on disk: 4098 MBytes
Encryption: disabled
In use by VMs: Win10 (UUID: xxxxxxxxxxxxxxxxxxxxx)
This is not the problem of VB, but the guest Windows OS does CACHE the disk. See https://forums.virtualbox.org/viewtopic.php?f=2&t=29136&p=439721#p130380
Once you restore the snapshot and restart the guest windows, please go offline and then online the writethrough disk (disconnect the drive and connect it back). For me, I will not use writethrough disk for windows guest again. I setup a hostonly network, and using smb (map network drive).
I hope the VB manual give a warning on this issue.