virtualbox.org

Does somebody know if there is a gain or loss of performance by using splitted VMDK HD instead of VDI in a VirtualBox VM?

This is because I intent to have a VM in an external USB HD to be used on both hosts WinXP and Ubuntu, thus I cannot format my external HD to either NTFS nor Ext3 because this will prevent me from using the VM in the host that does not support it natively (NTFS for WinXP and Ext3 for Ubuntu).
This way I had to use FAT32 and a 2G splitted VMDK HD (as VDI does not support splitting).

Any comments will be appreciated.

Regards,
Ricardo.

FAT32 is old, deprecated and should not be used any more. NTFS is fine on Linux with ntfs-3g. I used to run my VMs on that without any problems. Only thing you have to keep in mind is to NEVER defrag the partition that holds the VMs, as Windows can corrupt it's own file system when it's used together with Linux (been there, done that). A disk check may occur after the defrag and reboot back to Windows right after. You can always cancel this check, but if you do forget to skip it once, you might loose your VDIs. Same thing can happen for FAT32, but I haven't used FAT32 with big files, defragged it and then perform a disk check.

But, to answer your question:
There should be no difference in performance when using VDI or VMDK.

@Sasquatch: like it or not, FAT32 is still the universal standard for portable drives unless you really MUST have files >4GB. It has the advantage of being mature (people know how to give it adequate performance), and it's thoroughly documented, unlike NTFS. That means that non-Windows drivers for it don't have to rely on guesswork and reverse engineering (which is my way of saying that I'd be very wary about allowing a Linux NTFS driver to write to a drive of mine).

@ricardolucios:

ricardolucios wrote:This is because I intent to have a VM in an external USB HD to be used on both hosts WinXP and Ubuntu

The performance hit from running off an external USB drive will be more than enough to drown out any minor distinctions such as virtual image format, filesystem, filesystem fragmentation etc etc. By several orders.

I appreciate all your comments.

I share the same fears on making linux to write on an NTFS partition (even though I have lost data last time I did it ).
I also don't like the idea of not being able to defrag my NTFS partition, as we know fragmentation is one of the bad characteristic of NTFS partition.
Unfortunately I won't be able to run my VM on my internal HD due to disk space limitations, and I will have to live with the drawback of running the VM on a USB drive.

Thanks for all your comments!

Regards,
Ricardo.

If it has to be external, you might get better performance if it's connected through firewire (if the case supports it) or even better, eSATA. I have an eSATA drive that I can also use as internal hard drive and I don't notice any difference in performance whether it's connected internally, or through eSATA. Again, you need the hardware support for it.