Mirror Feature Provides Data Redundancy and/or Offsite Storage

A comprehensive data backup plan should include a backup copy of all your backup data. With Backup for Workgroups, you can use the Mirroring feature to backup your Data Repository to another group of storage devices. The Mirror gives you the ability to quickly recover your Data Repository in the event that a disaster occurs at your Data Repository computer. The Data Repository provides the on-site data storage and the Mirror provides the off-site data storage. 

The Storage panel shows how the Data Repository is stored on local D: and E: drives and the Mirror drives are located on a different computer on the same network:

Click to view full-size image

Mirroring Equipment

To mirror your Data Repository data, you will need mirroring equipment that has at least the same storage capacity as your Data Repository. You can always use a mirror hard drive with more storage capacity than your Data Repository, but you cannot use a smaller capacity hard drive. When you can mirror to a hard drive or appliance that is portable, you can fulfill your off-site storage disaster recovery strategy.

When you decide that you would like to mirror your Data Repository data, you can mirror to:

• A removable hard drive on the same computer
• A removable hard drive on a different computer
• A storage device (USB)
• A storage appliance (NAS)
• A hard drive on a separate computer (IDE or SATA)

Mirroring to a Removable Hard Drive on the Same Computer

An economical way to comply with your company’s off-site storage initiative is to install a removable hard drive on the same computer running your Backup for Workgroups Data Repository. With a removable hard drive on the same computer, you could mirror the Data Repository data to the removable drive and take the mirror off-site at the end of each workday. Add new drives that can be inserted into the removable drive cage to create backup rotation. Rotating the removable mirrors provides another layer of protection because one copy can always be stored off-site.

Mirroring to a Removable Hard Drive on a Different Computer

You do not need to install your removable media on the same computer running your Data Repository. The mirror can exist on any computer on your network that can be accessed through a share point available to the Data Repository.

Typically, you will find it necessary to power down the computer holding the removable drive before removing or rotating the media. You may want the removable mirror media installed on a different computer to avoid powering down the Data Repository.

Mirroring to a Storage Device or a Storage Appliance

Several third-party vendors offer plug-and-play storage appliances with large data capacity at attractive prices. Typically, these are small, stand-alone hard drives that attach to your computer through USB or FireWire, or they may connect to your network. You may decide to mirror your backup data to one of these storage appliances. These devices are handy because you can plug them in, perform the mirroring process, and unplug them to take off-site if desired.

Mirroring to a Hard Drive on a Separate Computer

You may already have servers that are being backed up by a third-party backup tool. You can use Backup for Workgroups to aggregate your backup data and mirror it to a server that is covered by this backup plan. To take advantage of your existing solution, use Backup for Workgroups to mirror your Data Repository data to a share point located on one of these existing computers.

Mirror Options

Depending upon the amount of backup data and the storage devices you choose to use for the Mirror, there are many options you can use to control the Mirror process.

Mirror Mode

When you only have one device inside your primary storage group and one device inside your mirror group, it does not matter which mirror mode you select.

But, when you have a mirror group that consists of more than one device/location, you can choose to correlate the mirror storage devices to a corresponding Data Repository device/location; which is referred to as an Interlocked Mirror. Or, you can choose to use the Mirror in an Ad-hoc mode, in which the mirroring process will replicate the files form any of the primary storage drives to any of the mirror drives based on available free space.

When Should I Use Interlocked Mode Mirrors?

If you want to have a 1-to-1 correspondence between each device in the primary storage group to a corresponding mirror device, you should select interlock mode. The primary advantage of using interlocked mirrors is if a primary storage device fails, you can replace the failed primary storage device with its corresponding mirror device.

When Should I Use Ad-Hoc Mode Mirrors?

If it is not convenient or practical for you to have a 1-to-1 correspondence between your primary storage group and mirror group devices, then select the Ad-Hoc mode. For example, your primary storage group device could be rather expensive and it is impractical to duplicate this in its entirety for the mirror. In this case, you may choose to use lower-cost storage for the mirror, and as a result, you might have more mirror devices than primary storage devices. An example of this would be if you plan to use a SAN or NAS device as your primary storage, but want to use a group of USB drives for portability in your mirror group.

What Happens If I Change Mirror Modes?

In the event that you change the mirror mode from one method to the other, Backup for Workgroups will perform a re-sync if necessary. This re-sync will realign the mirror storage to the primary storage; which may be very time-consuming.

Throttle

The goal of using the throttle options is to give you control over the speed at which the mirroring process occurs. By default, the mirroring process will consume as much bandwidth as available between the Data Repository Manager and the mirror device. If you want to prevent the mirroring process from consuming all the available bandwidth, use the "Limit the mirror update rate" option and specify a rate of your choosing. For example, if your mirror device is off-site, you may want a throttle speed that is half of your Internet link speed, to prevent the mirror process from consuming your Internet link.

Blackout

Use the Blackout feature to prevent the Mirror from consuming excess resources during business hours. For example, if the Mirror is located off-site, and you want to prevent the mirroring process from consuming your Internet link during business hours, you can set a blackout period to keep the mirroring process quiet.

Mirror Features

Use the Add, Modify, Remove, Pause, Options and Priority Up and Down buttons when you need to manage your Mirror Group.

Add Mirror - At any time, you can add more storage capacity to your Mirror Group. Please note that all storage evices within the Mirror Group must be online and accessible for the mirroring to occur; however, if any one of the Mirroring devices is offline, your backups will not be affected.

If you choose to use Interlocked Mirroring, you must have the same number of Mirroring devices as you do in the Primary Storage Group. In other words, if you have 2 devices in your Primary Storage Group, you must have 2 devices in your Mirror Group. And, with Interlocked Mirroring, the Mirroring drives need to have the same amount of storage capacity as their corresponding primary storage devices.

If you choose to use Ad-Hoc Mirroring, the sum of your Mirroring capacity needs to be greater than or equal to the total capacity of the Primary Storage Group. You do not need to match the same number of devices as you do if you were using the Interlocked Mirror.

Modify - You will need to use the Modify button accessible in the Mirror Group panel when a mirror device IS NOT accessible. Two common situations that may make a mirror device inaccessible occur when: (a) a USB device changes drive letters; and (b) a network share point experiences a change in name. When you press the Modify button, a dialog appears that allows you to change the name of the highlighted mirror device.

Remove - Use the Remove function when you want to stop using a particular mirror device and eliminate it from the Mirror Group. If you Remove all mirror devices, the mirroring function is turned off.

Pause - Use the Pause function when you want to temporarily disable the mirroring function. This is handy when you need to perform maintenance on one of your mirroring devices.

Options - Use the Options button to specify the Mirror Mode you want to use (Interlocked or Ad-hoc), change the throttle settings or specify a blackout period.

Priority Up / Down - When you are using Interlocked Mirroring, use the priority up and down buttons to match the order of your mirroring devices to correspond to the order of storage devices. Interlocked Mirroring replicates the first device in the Primary Storage Group to the first device listed in the Mirror Group, and so on through the list. In Ad-Hoc mode, the Primary Storage is copied to the Mirrors as a sum-total group, with priority given to the first mirroring device.

What is Not Mirrored?

Keep in mind that the Mirroring capability included in Backup for Workgroups is designed to mirror your backup data only. It should not be confused with a general purpose mirroring program. The Mirroring function does not cover ALL the data that resides on the computer hosting the Backup for Workgroups Data Repository. It does mirror the backup data that is stored in your Data Repository, but it does not capture anything else residing on this same computer. The Mirror can restore the Backup for Workgroups Data Repository only. It cannot restore the entire computer on which the Data Repository runs.