One useful feature of Virtual CD is the ability to create Virtual Blank DVD mediums of non-standard capacities.   This allows one to prepare images suitable for disc capacities that may become available in the future or to prepare an oversized disc if their DVD writer is capable of overburning recordable DVD discs.  One thing that we found unusual is that even though most DVD writers support CD overburning, but not DVD overburning, we are quite surprised Virtual CD only gave the options of 600MB, 650MB and 700MB as Virtual Blank CD capacities, yet a user defined capacity of up to 17.5GB for Virtual Blank DVD capacities.  So in this page, we will carry out some overburning tests to see if we can overburn virtual blank media with a standard capacity size and if we can also make use of the full capacity of a user-defined over-size DVD capacity.

Virtual CD-R media

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We carried out the following test using Nero CD speed’s Overburning test feature:

As we can see from the above screenshot, the Virtual Burner does not support the overburning of virtual CD-R media.  We tried again with Virtual blank 600MB and 650MB media, but with the same result as above once the write process reached their respective capacities.

Virtual DVD-R & DVD+R media

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While we can create a user-defined blank DVD+R of up to 17.5GB, in this test we will use standard size DVD-R and DVD+R capacity.  Like the issue we experienced earlier when creating data discs using Nero CD-DVD speed, this utility is incapable of testing the overburning of virtual blank DVD media either, as it gives the following error the moment we click ‘Start’:

So for this test, we used Nero to try overburning a virtual blank DVD-R by about 200MB:

However, just as it started the burn process, it displayed the following:

As 4,500MB is still larger than the standard DVD capacity of 4,483MB, we reduced the amount of content to burn to about 4,500MB and ran the burn process again: 

As we can see from the above screenshot, the Virtual Burner does not support the overburning of virtual blank standard size DVD-R media.  We ran this test again with a virtual blank standard size DVD+R, but with the same result.

User-defined Virtual DVD media size

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While we found that the Virtual Burner does not support overburning of standard size blank CD & DVD media, it does offer the ability to create blank DVD with a user-defined capacity.  The capacity can range anywhere from a mere 64MB all the way up to 17.5GB, for virtual DVD-R, DVD+R, DVD+R DL and DVD-RAM media.  Obviously, there is no 17.5GB single layer DVD media, let alone dual layer.

To start with, we will create a virtual blank 5GB DVD-R:

The following is the disc information tool reported by Nero InfoTool 5:

In Nero, we get the following disc info:

We then prepared a compilation of about 4,994MB in Nero and wrote the disc, which wrote and verified successfully:

The following is the properties for the Virtual DVD we just created:

Virtual Blank 17.5GB DVD Test

Now that we know Nero is capable of handling a DVD with a non-standard oversize capacity, in this test, we will try Nero with a non-standard 17.5GB Virtual DVD-R capacity, as well a non-standard 17.5GB DVD+R DL capacity. 

The following is the disc information reported by Nero InfoTool 5 for the DVD-R:

While there may not be a real blank DVD-R available with this capacity, Nero has no problem recognising this 17.5GB Virtual DVD-R:

We then prepared a compilation of about 17,500MB to fill the Virtual CD’s capacity and wrote the disc, which both wrote and verified successfully:

The following is the CD properties of this 17.5GB Virtual DVD-R we just created:

We repeated the process again, this time for a blank virtual 17.5GB DVD+R DL, which also burned and verified successfully:

As the timestamp of the “Burning Layer 2” is roughly midway between the “Burning Layer 1” timestamp and the “Burn process completed …” timestamp, it indicates that both virtual layers have roughly the same capacity.

User-defined Virtual DVD-RAM media size

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As a virtual DVD-RAM is effectively like the equivalent of a disk partition stored in a file, the ability to create user defined DVD-RAM capacities would have other uses besides just preparing virtual discs to later record on physical media.  For example, one could keep a set of DVD-RAM images to organise data, such as by project, without being restricted to the standard 4.7GB DVD-RAM size.  While archived files, such as Zip, Rar and Tar files also offer the ability to archive content into a single file, a Virtual DVD-RAM allows direct read & write access without having to extract or re-add files.  Like with an archive, it is also possible to password protect and encrypt the Virtual DVD-RAM data.

To start with, we will create a virtual DVD-RAM using the maximum user definable size of 17.5GB:

Once created and mounted, it is just a matter of formatting it:

This format process takes just a few seconds to complete, even without the “Quick Format” option ticked.  The following image shows the properties of this formatted virtual DVD-RAM:

Virtual DVD-RAM read/write performance

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While we know that a Virtual DVD-RAM drive will perform quicker than a physical DVD-RAM drive, in this test, we will compare the performance of Virtual DVD-RAM to hard drive performance in a couple of scenarios.  Besides acting as a virtual hard disk, a virtual DVD-RAM has the following advantages over archives and storing the data within a particular folder:

• All files stored within the DVD-RAM are contained within the DVD-RAM image files on the hard disk, thus reducing fragmentation.  If the hard disk containing the image is defragged, then most of the files contained within the DVD-RAM image are physically grouped together on the hard disk in 1.71GB (2 billion byte) files that make up the DVD-RAM image. 
• Unlike a file archive, the virtual DVD-RAM provides direct read & write access through a drive letter just like a physical DVD-RAM drive.  With a file archive, the files must be extracted first to open.  While Virtual CD does not provide a compression option for virtual DVD-RAM media, it is still possible to compress the image using NTFS file compression if the Virtual DVD-RAM image is stored on a drive using the NTFS file system.
• Virtual DVD-RAM can be password protected and encrypted to protect against unauthorised access.  It can also be write-protected to protect against accidental modification like with physical DVD-RAM media.
• If the Virtual DVD-RAM disc has a capacity of no larger than a standard DVD-RAM disc, it can be burned directly to a DVD-RAM disc for portability, while still retaining the exact file system structure. 

As a virtual DVD-RAM is one useful way of grouping files physically together on a hard disk and prevents cluttering the hard disk with small files, we have used the following two hard disk partitions to give real life hard drive scenarios below.  For these tests, we took a sample of 2.41GB of data consisting of 20,079 files and created a Tar archive (not compressed) using 7-zip and placed the tar file on a Hitachi 1TB drive on PC 1 and on a Western Digital 160GB drive on PC 2.  Before each time we extracted the archive to a drive to test, we rebooted the PC to minimise the effect of the cache affecting one test from the next.  We reboot the PC before we carry out the read tests to clear the cache from the write tests and then measure the time it takes to archive the contents into a new non compressed Tar archive on the original drive using 7-zip.

Virtual DVD-RAM 1 (PC 1)

• Placed on the first 40GB partition of a 160GB WD hard disk
• Hard disk fully defragged following creation of Virtual DVD-RAM
• Created with default capacity, formatted with FAT32 file system
• DVD-RAM image files contain no fragments

Virtual DVD-RAM 2 (PC 1)

• Placed on a 1TB Hitachi hard disk
• Hard disk filled to approx. 75% capacity
• Hard disk contains 7% total fragmentation
• Created with default capacity, formatted with FAT32 file system
• DVD-RAM images contain <10 fragments each

Virtual DVD-RAM 3 (PC 2)

• Placed on the first 20GB partition of a 74GB WD 10kRPM hard disk
• Hard disk partition filled to 67% capacity & 15% total fragmentation
• Created with default capacity, formatted with FAT32 file system
• DVD-RAM images contain ~1,330 fragments in total

Hard Disk 1 (PC 1)

• Western Digital Raptor IDE 10,000RPM, 74GB capacity
• 20GB partition at start of disk
• Hard disk partition filled to 67% capacity
• Partition contains 83,228 files and 20,748 folders
• Total fragmentation: 15%

Hard Disk 2 (PC 2)

• Seagate IDE 7,200RPM, 320GB capacity
• 80GB partition at middle of disk
• Hard disk partition filled to 81% capacity
• Partition contains 166,426 files and 13,444 files
• Total fragmentation: 26%

USB Flash drive (PC 1)

• Samsung 153x speed, 4GB capacity
• Policy set to “Optimise for Performance”
• Formatted in the NTFS file system
• Contains no data

Verbatim 5x DVD-RAM (MID: M01J5006)

• Optical drive: Pioneer DVR-112 on PC 1
• Formatted with FAT32 file system

Verbatim 5x DVD-RAM (MID: M01J5006)

• Optical drive: Pioneer DVR-112 on PC 1
• Formatted with UDF 1.5 file system

One clear thing the table shows is that Virtual DVD-RAM well outperforms the regular 5x DVD-RAM discs.  While the write speed performance does suffer to an extent compared to writing directly to the hard disk, particularly where the DVD-RAM image files are heavily fragmented, the read performance is quicker with the virtual DVD-RAM than individual files stored on the hard drive.  For example, the Virtual DVD-RAM 3 and Hard Disk 1 tests were carried out using the same partition on the same hard disk.

Despite all the hype over flash’s no seek-time feature, when it comes to writing a lot of files to Flash storage, at least to the USB flash drive we tested, it took roughly twice as long as it did with the slowest DVD-RAM test.  We decided to use the NTFS file system for the USB Flash drive test, based on quickest it took to copy the first 1,000 files to the flash drive when formatted in FAT32 and when formatted in NTFS.  When it comes to physical DVD-RAM media, the UDF 1.5 file system clearly outperforms the FAT32 file system when it comes to a lot of small files, but both are roughly comparable when it comes to read performance. 

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