Stripe Virtual Environments

For a specific project, I wanted to create a virtual ‘mini’ SharePoint farm so that DC, SP, and a 3^rd party app were running on different servers. Although the processor on the laptop was multi-core with hyper-threading and it had two large drives, I discovered that the physical HD is a performance bottleneck for such an environment because VM’s, each with two virtual HD, all try to access the same physical HD impacting on performance.

Saving the VM’s on different physical HD improves performance but copying the VM’s across disks is time consuming because of the large files involved. The disk access required by each VM may vary depending on type of project you are working on and so you may have to change the location of VM's. You may also need to change location if you have limited free disk space.

If you have a combination of multiple VM’s, some of which are part of different farms, then keeping track of these VM’s across multiple physical HD can become a problem. A better solution is needed.

The solution that worked for me is RAID 0 where data is striped across multiple disks (without redundancy or parity). As well as a large disk, even larger than any one physical drive, you also get the benefit of increased performance because each virtual HD is spread across multiple drives. You therefore do not have to worry about where to create your next VM.

Disclaimer

The aim of this article is to briefly describe the possible options available to you for using a striped disks for storing virtual machines. Most of these options are dependent on your hardware. Before changing the configuration of your computer make sure that you have performed necessary backups so that you are able to revert back to the original configuration if things go wrong. Note that performing a backup is not sufficient if you do not have the required software to perform the restore including OS, drivers, software, and license-keys.

I’ve deliberately avoided ‘how to’ steps here because I expect the person wanting to reconfigure their hardware to perform further analysis of the steps involved, the hardware required, and safety measures needed for their system.

Ensure that the hardware warranty is not invalidated by reconfiguring your computer.

Many hardware manufacturers create a special recovery partition on one hard drive that used restore the computer to factory defaults. You may want to ‘preserve’ this partition because it may be the only one that contains the valid licensed copy of your host OS.

Make changes at your risk.

There are a number of options available for creating striped configured disks:

• Through the BIOS


• Windows Dynamic Disks


• Disk Drivers

Below I briefly explain the advantages and disadvantages of each option.

Note that I refer to ‘drive’ as what Windows gives letters to like C: and ‘disk’ to the physical hardware that is partitioned and formatted.

Through the BIOS

In order to use this option, you will need two identical disks in your computer.

Advantages

Easy to configure new drives through the BIOS, including formatting them, because there is no need to consider saving existing data.

Might be possible to later bit-copy a normal disk to a striped configured disk. This may be necessary for example if you are upgrading a single disk system by installing two new identical disks in a striped configuration. The bit-copier software will see the new striped disk as a single large disk due to the BIOS. For the same reason the OS should also boot without requiring additional drivers.

Disadvantages

Configuration is performed through the BIOS before the host operating system is installed and therefore it is not a conversion or upgrade of an existing system.

For a new Windows OS install you may need to provide additional drivers (F6 option) if you are not going to use a bit-copier.

If you’re using a laptop then the it may not have the required hardware and BIOS support.

Windows Dynamic Disks

To use this option, you will need a Professional Edition of Windows OS as the Home Editions do not support this feature. Existing simple disks will need to be converted to dynamic disks that would allow creation of arbitrary volumes on the same disk without the partition limitation of simple disks. Dynamic disks allow creation of volumes on free space which need not be a single consecutive block of disk.

After the conversion the drive containing the OS (which is usually the C: drive) cannot be changed to a striped disk. The disk containing the OS needs to be 'shrunk' to create space for new volumes. An equal amount of space is also needed on another drive before a striped volume is created.

Advantages

You can configure using a Windows interface instead of using the BIOS.

You may change your mind by removing and recreating new volumes by either moving existing data around or backup-and-restore.

Not necessary to have identical physical drives.

Can convert a standard disk to a dynamic disk including the system disk.

Disadvantages

Not easy to convert a dynamic disk to a simple disk in case you change your mind.

You have to create volumes on separate disks (to have RAID 0) that will be used by the striped drive and because your OS is already installed on one disk, the maximum space you may configure for the striped volume depends on how much free space you leave on the OS drive – too little and you may run into problems.

Disk Drivers

These are device drivers supplied by hardware manufacturers for Windows OS. In addition to the drivers, utilities are provided to configure the hardware that may run within Windows OS.

Advantages

Like Dynamic Disks, you may be able to configure your hardware after the Windows OS is loaded using a Windows interface instead of using the BIOS.

You may be able reconfigure an existing system without having to reload the operating system. I’ve personally not done this but I assume you may not be able to convert the volume on which Windows OS is running.

Such drivers claim to improve SATA disk performance in addition to supporting RAID 0.

Disadvantages

Your computer needs have the necessary hardware support and those that have it may also provide the BIOS support for RAID 0 configuration. You cannot upgrade the chipset without upgrading the system-board.

There may be limited support for your hardware manufacturer, perform internet searches to see what kind of problems others have encountered and the level of support you can expect.