Page 3 of 3

Re: Could not get the storage format of the medium

PostPosted: 26. Dec 2015, 01:44
by davidbaumann
So I am right sure, it does what I mean, because the effect is like expectet.
No "discard=on", and I cannot run fstrim in my guest.
With "discard=on" I can run fstrim, it shrinks the vdi automatically, which is quite useful for me.

I also know, how to trim manually, which needs action and takes time.
So why are you shocked I am using a feature that worked. I am shocked, this discussion doesn't really help me.

It rather should lead to some devs to correct the documentation, or deprace/disable the feature.

Re: Could not get the storage format of the medium

PostPosted: 26. Dec 2015, 10:55
by mpack
I had hoped for something better than a brainless blogger as justification for this.

davidbaumann wrote:It rather should lead to some devs to correct the documentation, or deprace/disable the feature.

Sometimes the devs partially implement a feature and then don't document it because it was incomplete at the time of the next maintenance update. And, if you want to use undocumented features you can't claim that they didn't behave as documented.

I would also suggest relying on the official manual, not online bloggers who give no references for their discoveries, nor indications of affected software versions.

Re: Could not get the storage format of the medium

PostPosted: 26. Dec 2015, 10:58
by mpack
socratis wrote:Well, first of all (as one green-hat told me), I am shocked, shocked I'm telling you that people will follow online blogs and will not follow the instructions in the manual on how to compact a disk.

I'm pleased that people still understand the reference - it is after all from a 1942 movie. :D

Re: Could not get the storage format of the medium

PostPosted: 26. Dec 2015, 11:04
by socratis
I think this is the beginning of a beautiful friendship... ;)

Re: Could not get the storage format of the medium

PostPosted: 26. Dec 2015, 11:18
by socratis
davidbaumann wrote:So I am right sure, it does what I mean, because the effect is like expectet.

So, you expected to lose your VDI? Really? And the "I'm sure" part, I'm sorry, I don't get it. You followed blindly an unknown blogger's advice, with no other references. Yet, you were sure that it worked. Beats me...

davidbaumann wrote:With "discard=on" I can run fstrim, it shrinks the vdi automatically, which is quite useful for me.
I also know, how to trim manually, which needs action and takes time.

Both of these actions require user intervention. The thing is that one of then is well tried and documented, while the other is so "experimental" that the developers didn't even document it. Kind of like an unpublished API that some people use and when it is removed/modified and their app breaks, they complain.

davidbaumann wrote:I am shocked, this discussion doesn't really help me.

Correct me if I'm wrong, but I wasn't the one that started this discussion. And the only help pretty much you're going to get from the majority of the users in these forums, when you're dealing with a VERR_VD_IMAGE_REPAIR_IMPOSSIBLE, is to hope that you have a recent backup.

Re: Could not get the storage format of the medium

PostPosted: 26. Dec 2015, 11:27
by mpack
@David: no more substantial help is possible until I have the VDI segment and information on file size, as requested some time ago now. At the moment we're just chatting aimlessly until that info is provided. The speed at which something useful (or at least definitive) happens is up to you.

Re: Could not get the storage format of the medium

PostPosted: 26. Dec 2015, 11:33
by mpack
p.s. I see that you commented in another thread: https://forums.virtualbox.org/viewtopic.php?f=7&t=51768

I'm surprised you didn't mention this, because now you have found an authoratative source (Aeichner is one of the devs). The first two posts in that topic in particular are useful. Still, the fact remains that the devs chose not to document it yet, though it wouldn't be the first time that the manual has proved wanting.

I see that the feature requires (virtual) SCSI or SATA. Is that the case in your VM?

Re: Could not get the storage format of the medium

PostPosted: 31. Dec 2015, 02:06
by davidbaumann
So it's an SATA controller with AHCI enabled, yes.

I added a reference to the other post, you are right, I should have mentioned.

Size of the broken one: 85194916
Size of the working one: 26101880

Also, I attached the first 3MB of the VDI files.

So actually, I don't have a Backup of the Box, it's just Windows 7 and some programs. Actually they take time to install, but that's no real problem.
But maybe it's just a wrong integer value in the header, who knows.

I will also open the file with the Windows Tool which was linked earlier later.

Still, thank you for explaining and helping me.

Re: Could not get the storage format of the medium

PostPosted: 31. Dec 2015, 11:28
by mpack
davidbaumann wrote:Size of the broken one: 85194916
Size of the working one: 26101880

26meg (24MB) for a working Win7-64bit installation? I think not!

Also, I'm confused as to why did you provided me with the "working" file at all? I didn't ask for one: obviously I have plenty of working VDIs already. Are you saying this VDI is related to the broken one in some way?


As to the broken VDI, it seems to be really messed up. It is not just a corrupted header: the first first entry in the block map is garbage too, who knows how many others. The header looks like it has been overwritten by more blockmap, and then some of the fields were replaced by correct values. In particular it has the correct blockmap and image offsets, but if I view the file at the latter offset expecting to see an MBR sector, I see an NTFS boot sector instead (the sector that's found at the start of a bootable NTFS partition).

Also, this VDI seems quite old - it's still using 4K alignments, which was changed to 1MB alignments 3 years ago. It would have been nice if backups had been made in that time.

I don't think anything can be done here. It's a mess.

Re: Could not get the storage format of the medium

PostPosted: 31. Dec 2015, 14:22
by davidbaumann
I think I created the boxes with VirtualBox 4.3.34 or even earlier. And actually, I don't have a Backup ;)

So what about doing the command? Should it be included to documentation, with a warning? Or do nothing?

Re: Could not get the storage format of the medium

PostPosted: 31. Dec 2015, 14:28
by mpack
Since the official manual contains no explanation of the command that I can find, then I don't know why anyone would ever use it. No doubt the devs will document it better if and when the functionality has been completed and tested.