Recently a guest VM goes to Guru Meditation state with a critical error instead of starting normally

Discussions related to using VirtualBox on Linux hosts.
milverton
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Joined: 17. Apr 2022, 22:25

Re: Recently a guest VM goes to Guru Meditation state with a critical error instead of starting norm

Post by milverton »

mpack wrote:A dynamic VDI is just a file on the host. Not in any way special nor especially complex compared to other host files.
mpack, Your thought on this has been going round in my head, and at first I was totally in agreement with you, as I said earlier. But I'm now thinking: could there be a way of countering your thought? So, I'd like to ask you: let's strike through the word dynamic for a moment, and perhaps reconsider whether a VDI file is, as you suggest, just a file on the host.

"On" the host it undeniably is, but "of" the file system used by the host it can hardly be, if it is to be transferable between Virtualbox installations running under different OSes. I put it to you: there might be only one environment in which the range of different types of vdi file are truly welcome; namely the kind of inner sanctum created by the designers of Virtualbox.

Stay with my thought for a moment, and then consider how software running under any given OS would be able to determine if the hard disk sectors used by such a file were 'valid" - to use a term found deep within the operating manual for Diskgenius... but used without any elucidation as to what the word means - or what the implied technical algorithms are - in the context the manual writers are using it.

At any rate, I've now digested that it's critical to use an "All Sectors" setting with Diskgenius. The pursuit of the reason why this makes a difference is very possibly holding the clue needed to unravel the puzzle of whether the vdi data sectors [I've not been able to recover so far] were backed up; and if they were, then where to and how. And might also shed some light on why it seems that a 32-bit WIndows VM can emerge unscathed from the backup/restore of the Linux partition while 64-bit Windows VMs can"t [with the "All Files" Diskgenius setting].

The fixed versus dynamic question might be a red herring, but the 64-bit versus 32-bit question somehow might have significance.
scottgus1
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Re: Recently a guest VM goes to Guru Meditation state with a critical error instead of starting norm

Post by scottgus1 »

If I might weigh in on that question, Milverton, no, a dynamic disk file wont be any different than a fixed disk file, if DiskGenius interprets the file correctly.

If I have a text file containing the text "The quick brown fox jumps over the lazy dog" or a jpg of my family, that text file or the picture must remain the same bits regardless of what file system it's stored on, or to what file system it gets transferred to. My family should still look the same, and the fox should still jump the dog, regardless of FAT#, NTFS, EXT#, HFS, ZFS, etc.

Same thing with vdi's, dynamic or fixed-size. A disk file is also a picture, like a jpg, it's just a picture of an OS. That picture is and should remain the same regardless of what file system it's stored under, just like the family pic and the fox.

A file system is only a way to organize the data in the files on the physical disk. But the data does not change when switching to a different file system. Dynamic vs fixed-size should make no difference.

However, if the backup software is a little too 'genius' (which means buggy), then it might get itself into trouble if it is reading through the data to copy and takes it upon itself to interpret the data. For example if it's reading through an EXT# partition then finds a file that looks remarkably like an NTFS partition, and that's what it would see when reading the Windows VM on the Linux side of the dual-boot, that might trigger a bug and cause interference between the EXT# and NTFS interpreters, and record bad data.

I'm sorry if you've stated this and I've missed it: Have you tried backing up both a dynamic and a fixed-size vdi, and see if one or the other or both get corrupted in the restore?

If not, here's an experiment:

Make a small VM on a fixed-size drive. Use Mpack's CloneVDI to make a dynamic-size clone of the VM's disk file, and set it up in a VM, too. Ensure they both boot up correctly.

Now, run a DiskGenius backup of both drive files with the valid test enabled, and see if the drive files restore correctly to a different folder.
mpack
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Re: Recently a guest VM goes to Guru Meditation state with a critical error instead of starting norm

Post by mpack »

I may be missing it, and I know nothing about Disk Genius, but I have seen nothing to indicate that this host backup tool has any ability to inspect the contents of a VDI and determine what sectors are used and which are not. Even VirtualBox does not have that ability. Nor is it credible to me that this tool will mount random VDIs it finds into the host filesystem so that the host OS can interpret the contents of a guest filesystem. That would be a wildly inappropriate interference in the workings of other software. Would you expect it to open Office documents to check the spelling?

So unless I've misunderstood and we are discussing backup software that runs inside the guest, then all this talk about guest filesystems is all red herring. A VDI is just an ordinary file to the host - so the only question is whether this file was ever backed up.
fth0
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Re: Recently a guest VM goes to Guru Meditation state with a critical error instead of starting norm

Post by fth0 »

milverton wrote:
fth0 wrote:After starting a QEMU/KVM VM in the background ('&'), the kvm_intel module is in use,
Is this something you did by starting a particular VM? or how did this happen?
The QEMU command in my example simply started an 'empty' VM (without virtual hard disk or virtual DVD), which only ran its virtual BIOS and then waited forever. Its sole purpose was to demonstrate the difference in the lsmod output.

In your setup, kvm_amd was not in use when you checked for it, so there is nothing more to look for in this situation.

Regarding the Guru Meditation, I don't understand the real cause so far. There's a triple fault after reading ~400 kB from the virtual hard disk.
milverton
Posts: 48
Joined: 17. Apr 2022, 22:25

Re: Recently a guest VM goes to Guru Meditation state with a critical error instead of starting norm

Post by milverton »

mpack,
Thank you for the response on the vdi file sectors question.

scottgus1,
The fixed versus dynamic issue is very much on the back burner at the moment.

mpack, scottgus1 and fth0,
One simple thing I'd like to try is again restoring the oldest backup I have of the Linux partition, now that I have entered the license key into Diskgenius on the HP Envy x360. After all, it was during the restore operations that the mysterious error messages appeared.
milverton wrote:during restoring the parftition from image backups done with the default setting of "All Files", the process did not go flawlessly: there were a number of errors reported. They didn't stop the proces, though. They all had exactly the same wording, namely
  • "Write disk error."Note: Error has been omitted. The restored data will have errors.
This happened in batches at different stages during the backup The count of those exact errors was about 30; or, in two runs, about 120.
I need to take time out before I can run more tests, including those suggested by scottgus1 and fth0, but will be back in a few days.
fth0
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Re: Recently a guest VM goes to Guru Meditation state with a critical error instead of starting norm

Post by fth0 »

Just in case it's not clear, I haven't suggested any further tests to perform.
milverton
Posts: 48
Joined: 17. Apr 2022, 22:25

Re: Recently a guest VM goes to Guru Meditation state with a critical error instead of starting norm

Post by milverton »

This post is a follow-up after running the experiment suggested by scottgus1.
scottgus1 wrote:...here's an experiment:

Make a small VM on a fixed-size drive. Use Mpack's CloneVDI to make a dynamic-size clone of the VM's disk file, and set it up in a VM, too. Ensure they both boot up correctly.

Now, run a DiskGenius (henceforth DG) backup of both drive files with the valid test enabled, and see if the drive files restore correctly to a different folder.
Test-VMs were prepared for this experiment. The method used followed scottgus1's suggestion namely:
- a basic VM was constructed using the "Fixed" option for its VDI.
- mpack's VDI-cloning tool VDIClone4-1 was used to clone just the VDI. The clone the tool produces is by nature "Dynamic". (The tool was a joy to use and did the job perfectly, by the way.)
- a new VM was constructed to use the cloned VDI, with each and every other VM setting set to match the first.

In practice the process was doubled because 1 32-bit VM and 1 64-bit VM were constructed.
- The 32-bit VM contained Windows XP Professional Service Pack 3.
- The 64-bit VM contained Windows 7 Professional Service Pack 1.

The main purpose of the test was to resolve whether making a full image backup of the Linux/Ubuntu partition using Diskgenius resulted in any of the 4 VDI files becoming corrupted. Of interest is that DG has 3 settings, affecting what it backs up, to choose from before making a partition backup image. (It also has 4 settings affecting the level of compression used; but the default of "Normal" compression was set throughout this experiment.)

3 partition image backups of the Linux/Ubuntu partition were done in succession, using the 3 different DG settings of interest. They are (in the order done):

- All Files;
- Data Sectors;
- All Sectors.

To recap somewhat, at the start of this topic only the All Files setting had been used, though unwittingly rather than deliberately. This setting scottgus1 charaterizes as the one "with the valid test enabled". In this experiment it was successful only for the 32-bit VM with the dynamic VDI; not for the other 3 VMs.

Later I discovered the existence of the DG settings and tried the All Sectors setting, which does not use any "valid test". Backing up using All Sectors turned out to be successful for all 4 VMs in this experiment.

The above 2 results were useful in confirming experience documented earlier in this topic.

In this experiment I have included the Data Sectors setting, which was untried until now. DG says it also uses a "valid test". Unknown is whether its valid test is identical, but anyway it turns out that Data Sectors is also successful for all 4 VMs in this experiment.

Since mpack has suggested the size of the files generally could be an undisclosed factor included in DG's "valid test(s)", helping DG determine whether to back them up or skip them, the size of the VDI files in this experiment is given here, in order of size:
- 32bit dynamic 1,699,741,696 bytes (1.583 GB)
- 32bit fixed 3,223,322,624 bytes (3.0 GB)
- 64bit dynamic 14,437,842,944 bytes (13.446 GB)
- 64bit fixed 25,771,900,928 bytes (24.0 GB)

Again, to clarify, although the discussion has been about VMs and VDI files, the backups and restores are of complete Linux/Ubuntu partitions done from the adjacent Windows 10 partition using Diskgenius.

Experiment progress was documented using VM screenshot images for the 3 backups which did not result in successful restores, together with log files before all backups and after all restores; and I planned to group them in a meaningful way and attach them, but was foiled in that regard by the Forum's 128kB limit, even with zipping. If anyone would like a particular log file (or a pair of them for comparison), do please ask and I will attach them to another post.
milverton
Posts: 48
Joined: 17. Apr 2022, 22:25

Re: Recently a guest VM goes to Guru Meditation state with a critical error instead of starting norm

Post by milverton »

mpack wrote:...so the only question is whether this file was ever backed up.
mpack, I'm pretty sure now that all the vdi files, including all the ones back to the beginning of this topic, were backed up as part of the entire Linux/Ubuntu partition: just not in a way which is intelligible to Oracle's Virtualbox after the partition is restored. Although the 32-bit dynamic VDI is the only one which survived intact, there does seem to be real data in all of them. Still working on that, though, to see if recovery is possible. There is a tool put out by Aryson Tehnologies specifically to work forensically with corrupted vdi files. One of its modes is called "Deep". I'd be interested whether anyone has experience with it.
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