In the first article in this two-part Storage Basic series, we looked at some of the general backup procedures used to manage the process of backing up large amounts of data. In this article we dig a little deeper into backup strategies, specifically looking at LAN-free and server-free backups and how they are used to eliminate the backup window. First, though, we’ll review two types of network designs and how they impact backup traffic.
When designing a network, careful consideration must be given to the location of backup devices, as their physical placement on a network has both performance and security implications. In a traditional network design, a backup device is located on the same segment as all of the other network devices.
As you might imagine, there are both advantages and disadvantages to this approach. When network devices are on the same segment as the backup device, it’s relatively easy to configure all network devices, including workstations, to back up to the backup device. It’s also a low-cost solution, as backup devices can be added to a segment without major changes to the network infrastructure.
However, because the backup device is on the same segment, there’s a greater security risk, as workstations may be able to directly access the backup server. Furthermore, if backup devices are located on the same segment, the volume of backup data being transferred can negatively impact the speed of the network. This is why backups are often performed in the off hours to prevent impacting network users. As discussed in the first part of this backup basics series, this creates the problem of the “backup window.”
Removing Backup from the LAN
For those organizations that transfer huge amounts of backup traffic, there is another option — physically remove the backup device from the LAN. In this scenario, the backup device is located on a dedicated Fibre Channel segment. This network design is typically more secure, as access from Ethernet network devices can be limited and controlled by the storage or network administrator.
Perhaps the greatest benefit of removing the backup device from the production LAN is in performance. LAN bandwidth is preserved for the production network, and backups can be performed at any time without impacting users.
On the downside, when backup traffic is taken off the regular LAN and placed on a high-speed alternative, it can be costly in terms of both dollars and administrative overhead. However, when in place, it provides the ability to provide two unique backup strategies: a LAN-free backup and a server-free backup.
In early storage development, a common backup strategy was to have backups performed to locally attached tape devices. For larger network environments, this approach had two significant drawbacks — cost and management. Maintaining a large number of decentralized tape drives and media became difficult and inefficient. This lead to the development of software that allowed designated servers to act as centralized storage devices. While this approach allowed backups to be managed from a central location, it also meant that all backup traffic had to travel over the LAN to the backup server.
In many environments, this can still be an effective backup design as long as the LAN can support the amount of traffic that the backups generate. However, in many of today’s modern environments, the amount of backup traffic that must cross the LAN is simply too great for the LAN regardless of the LAN technology used. The solution in this case is to take the data off of the LAN.
The LAN-Free Backup Solution
A LAN-free backup solution allows you to use a storage area network (SAN) to create a shared, centralized backup and recovery point. It offers the management capabilities of a centralized backup solution while at the same time also delivering the performance of distributed backup solutions. LAN-free backups take the backup traffic off of the LAN by using dedicated links to network servers with centralized storage devices.
Each server maintaining data that must be backed up requires a Fibre Channel adapter that connects to a Fibre Channel hub or switch. The hub or switch is connected to a tape library or disk array.
In this configuration, a single server, or server cluster, can act as the central backup point for all servers on the network. All backup traffic travels through dedicated high-speed links, reducing the load on the regular LAN links and all but eliminating the limitations of the backup window.
The Server-Free Backup Solution
LAN-free backups increase backup speeds and centralize management, but what if it were possible to take backups one step further and transfer backup data directly from disk to tape without using a server? This option is known as a server-free backup.
When we talk about a server-free backup, we are referring to a process where the backup data path does not go through a server. While a server is needed to control the overall process and maintain the backup software, data is passed between disk and backup library without requiring a server’s CPU. This frees server resources to be used elsewhere on the production LAN.
There are several advantages to implementing a server-free backup solution, including offloading traffic from the LAN, reducing the load on server system resources, and high-speed data transfer. As with most areas of technology, though, there are also a few drawbacks. A server-free backup solution is more costly and complex to design and manage, and when something goes wrong, they can be very difficult to troubleshoot.
Other Backup Alternatives
While a LAN-free or server-free backup solution may be the answer to eliminating the backup window issue, they are often too costly for many organizations to implement. This can lead to rather creative methods of increasing the speed of the backup process or working within limited backup windows.
One method that keeps surfacing is replacing tape with hard disks, as backups to disks are faster. While there isn’t the space in this article to fully explore the tape vs. hard disk debate, we can say that in most environments, tape is still the leader. While hard disks are able to store and retrieve data faster than tape and provide real-time transmissions, tape media is the clear choice in terms of better portability and security. While hard disk transfers may be faster, newer tape devices are able to transfer large amounts of data at reasonable speeds.
Tape backups do have some drawbacks, including a shorter media and drive lifetime than their hard disk counterparts. Hard disks, however, are often viewed as a security vulnerability point, as data on the hard disk can be live and accessible to the network. Still, if the backup window for a network is a real concern and time is critical, a combination of tape and hard disk backups may be the solution.
In summary, coping with the issue of the backup window can be a costly endeavor for an organization. As the traffic generated by backups continues to grow, solutions will be needed that can handle the load without disruption to the production LAN. While some band-aid solutions, such as hard disk backups, may buy some time, the trend is certainly toward taking the backup traffic off of the LAN.
LAN-free backups allow network servers to share tape libraries and also allow faster backups than would be possible when backing up using a regular LAN. With the majority of backup traffic removed from the LAN, the LAN is free for other uses. Server-free backups take this one step further by taking backup traffic away from the server and transferring directly from disk to tape.