problem with large file access v. 4.1.4

[molau]

Hello,

I've been using Virtual Box for about two years now, running Win7 64 bit as host and XP 32 bit as guest OS. Data and applications I'm working on are not stored on the virtual disc, but instead I'm working on the host drive mapped as network drive inside the virtual machine. I upgraded virtual box several times inbetween and everything was fine up to the last version 4.0.12-72916 with extention pack 4.0.4-20112.
A few weeks ago I upgraded to the latest version 4.1.4-74291 with extention pack of the same version.
At some later time I experienced occasional problems and did not know where they came from:

* when running Total Commander and trying to read a larger text file (few hundred kB) with the internal viewer, I would simply receive a "read error"
* when trying to open the same text file with Notepad++, I would get no error message but simply an empty file
* one of my own C application would not work anymore. Debugging in Visual Studio revealed that a simple file read operation
numcatstars=fread(catalog,sizeof(catstar),MaxCatStars,f);
that had not been touched for years would suddenly return zero records. When executing the same program locally at the virtual hard disc, the problem disappeared
* when compiling the same program, visual studio complained that it could not embedd the manifest anymore into the assembly

Only today I realized, that all problems may be related to the same file access issue. For testing I downgraded to the previous 4.0.4 version, and the problems were gone.

Is this a known issue?

Best,
Sirko

[frank]

Where are the files located, on shared folders or on the virtual disk?

[molau]

The problems occurs only when the files are on the shared folder. There is no problems if files on the "local" virtual disc are accessed.

[mpack]

Any by shared folders you mean true network shares, not GA shared folders?

[stefan.becker]

Shared Folder on external USB drive with FAT32?

[molau]

By shared folder I mean those offered in the virtual machine configuration.
I configure the local Win7 NTFS C:\ hard drive as C_DRIVE share, and inside the virtual machine I do effectively a
net use M: \\Vboxsvr\c_drive
While working on M:\ I observe the problems, but not when working on C:\ of the virtual machine.

I hope that is not too confusing.

[mpack]

And are you sure this has been working a long time? I mean specifically accessing a VBox shared folder using your code - I'm sure your code is known to work in other scenarios. I have had similar problems reported by people using my software to read/write files contained in VBox shared folders - but the problem has been there a long time, it isn't a new problem in v4.1.4. The reports didn't identify "large file" as a requirement, but the files would have been large anyway, so it makes sense.

Anyway, my solution would be to try a proper network share. Designate a shared folder on your host, make sure host and guest belong to the same workgroup. Use host-only or bridged networking in the guest, as I don't think NAT will work for this. You should then find the share from your network neighbourhood inside the guest. You can map it to a drive letter as before.

[molau]

I have been working with this configuration for over a year now and never experienced problems. The problems with other standard software that has not been updated (Total Commander, Notepad++) occured occasionally in the last few weeks. I did not care about it until last week when I found, that even my own software did not work anymore. Of course, I was first checking which bug I had introduced recently, until I found that a simple read operation would fail and that the software was running fine on another (physical) XP machine, and even inside the virtual machine on the local drive. Only then I realized, that all problems may have the same root cause, and tried a rollback to the previous version of virtual box / extension pack. After the downgrade (leaving the VM configuration untouched), the problems with Total Commander, Notepad++ and my own code immeditely disappeared.

As network adapter I use PCnet FAST II (NAT). If my memory is right, I have tested other network sharing methods when I started with VirtualBox, but this one gave the best performance when copying many files etc. In fact, it was faster than MS Virtual PC and VMware player, which is why I finally decided for VirtualBox.

[mpack]

I have tested other network sharing methods when I started with VirtualBox, but this one gave the best performance when copying many files etc.

That would be a very unusual result... I think most people around here would agree that top performance comes from a true network share as I described, while using VirtIO-net network drivers inside the guest. Details in chap6 of the user manual. The GAs are very convenient to use, provided the guest OS is supported of course, but they are not the top performers.

[molau]

Ok, I will try that once more time permitting.
The host drive is shared, anyway, so I only have to modify the network adapter and create a new network drive in the VM. I take for granted that I can then still access the Internet from the virtual client through the host's DSL connection?

[mpack]

Take nothing for granted.

If you use bridged then you have internet access via the host, as well as access to the host itself. If you use "host only" then obviously you don't have internet access. However, another possibility is to use two NICs: host only on one to provide shared folder access, the other NIC used in NAT mode for basic internet. You would only tend to use the second more complicated setup if you have a good reason, e.g. your PC is connected to employers server, and it will not like it if your VM gatecrashes the network (bridged means that the VM appears on the network, in NAT mode that doesn't happen as all network traffic is relayed by the host).

[Perryg]

I don't and have not for some time used anything but the VirtIO-net network drivers. The speed is so much faster it is worth the extra effort to install the drivers in Windows. Most Linux based OSes have them built in already.

[molau]

One more question: To be honest i dodn't know what to give as VBox-Version. I know what my host and VM OS are, but Vbox version? Do I find this somewhere under "Help" or so?

[molau]

I don't and have not for some time used anything but the VirtIO-net network drivers. The speed is so much faster it is worth the extra effort to install the drivers in Windows. Most Linux based OSes have them built in already.

Hmm, do I get you right that you suggest to use the shared folder function of VBox (as I'm currently doing)?
Of course, I installed the host extensions.

[mpack]

VirtIO-net is not an option with GA shared folders, so no, that can't be what Perry is suggesting.