VM Recovery

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Frequently asked questions about VM data recovery


VMware boot image corrupted?

During install ESXi Server creates several FAT partitions for it’s system purposes and forbid access to these partitions to any 3-rd party software. One of these partitions used to store image of the ESXi Server. During boot of ESXi Server it creates a RAM disk, loads stored image from forementioned FAT and proceed to the system boot from RAM disk. Also, there are multiple checks of integrity of the stored boot image, and effectively prevent it’s corruption.

Should you have any issues with such error, it may be caused by either updates or hardware. Especially RAM modules as they are the actual disk media for the boot image. If it’s software to blame, try to reinstall ESXi Server.

VMFS volume not mounted?

If VMFS volume not mounted, try to use ESX Service console or Direct console (ESXi). Please note that console is to be enabled before use in Server’s options. To mount VMFS volume use ESXCLI or vicfg-volume commands:


To list all volumes that have been detected as snapshots:

esxcli <conn_options> storage filesystem list

Mount a volume:

esxcli <conn_options> storage filesystem volume mount --volume-label=<label>|--volume-uuid=<VMFS-UUID>

To unmount a volume:

esxcli <conn_options> storage filesystem volume unmount --volume-label=<label>|--volume-uuid=<VMFS-UUID>


To list all available volumes:

vicfg-volume <conn_options> --list

To mount a volume:

vicfg-volume <conn_options>  --persistent-mount <VMFS-UUID|label>

Unmount a volume:

vicfg-volume <conn_options> --unmount <VMFS-UUID|label>

Also, you can use VMFS Recovery to access VMFS volume. As we use direct disk access, we do not require VMFS volume to be mounted or ESX server running at all. Connect HDDs as local hard drives or use SSH\iSCSI to access data on the server.

VMDK file not recognized?

A common error when *.flat.vmdk misses it’s descriptor file, a small text *.vmdk. ESX require both files to exist in same directory and have corresponding names. Vsphere moves both files by default and also may add necessary changes to configuration files for proper work of VM in a new location. However if you have used SSH and forgot to copy descriptor files, you may create a new VM disk with same name and features that had one with lost descriptor and then change new *.flat.VMDK with an older one.

Need to recover VMDK file?

If VMDK file can not be found on the disk, you need to run VMFS recovery in Uneraser or Full Recovery-> VMFS modes and check if data is recoverable. Demo version is able to mount recovered VMDK files and preview files inside VM to make sure that integrity is preserved.

vSphere: Unable to read partition?

Such problem is normally caused when partition table doesn’t comply to MS-DOS partitioning standard or 0-th track is corrupt.

Solution would be format HDD in MS-DOS compatible layout. If format command fails or there are valuable data present on the disk, you need to proceed to recovery. We strongly recommend to create a disk image from such drives in order to reduce load on the damaged disk and stop further possible degradation. After creating a disk image, mount it to VMFS Recovery, scan in Reader\Uneraser\Full Recovery modes and check integrity of recovered data.

ESXi could not read volume header?

Most probable cause of this error is a formatted or heavily damaged VMFS disk. At this case you need to run VMFS recovery in Uneraser or Full Recovery-> VMFS modes and check if data is recoverable. Demo version can mount recovered VMDK files to it’s disk list and allow preview files inside VM to make sure that integrity is preserved.

VMFS datastore inaccessible?


ESX Server datastore not visible?

There are too many possible reasons, that may cause such issue. You need to narrow possibilities by checking hardware and software configuration. Check if hardware works fine using server logs and monitoring and proceed to software.

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