Working With SAN Backup Solutions

by Rod Dunne on July 26, 2010

in Backup Software, Data Recovery

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Using SAN backup solutions forces you to consider a variety of scalability, disaster recovery and bandwidth demands that affect the architecture of your network. Here, we’ll look at some of the benefits and pitfalls of using this network configuration along with tape backup systems.

At its core, a storage area network (SAN) uses an Ethernet switch (iSCSI-capable NICs) or fibre channel switch to connect together a number of servers, online disks and offline tapes or optical devices. Each of the servers then has read/write access to any disk/device on the SAN without needing to go via the LAN (local area network).

Benefits

Scalability: As your IT infrastructure grows, the network can add additional SAN tape backup devices or disk backup storage.The SAN takes on the large data volumes that would have otherwise put a strain on the LAN.

In comparison, the old backup tapes were fine for small data centers (one server per tape) but it didn’t scale up. The newer architectures still regularly use a SAN tape backup as an safeguarding measure if the network should go down completely.

Mirroring: Any servers that have their disk storage on the network can easily make SAN backups by mirroring the server and making the clone available to your backup server. Some NAS backup solutions can also provide mirroring support.

Booting Servers From The SAN: In some enterprise data center setups, each server can boot from SAN backups if an existing configuration develops a fault. This requires specialist software to allow the SAN to swap between faulty and replacement servers as and when they are needed.

Remote Backups: Backup storage can be stored locally and remotely in order to facilitate disaster recovery. A remote backup server can be communicated with using Fibre Channel over IP. The cost of IP WANs is cheap in comparison to offsite tape storage and the transfer times obviously faster (than retrieving backup tapes from an offsite storage facility). Modern complex systems use disk array controllers/servers to implement storage replication between the various sites and further automate the backup process.

Pitfalls

Network Uploads: SAN backup solutions really took off because data centers were growing in size and it became unwieldy to support local tape backup machines for each server (the volume of tapes also takes up a growing amount of space). However, as the SAN data volumes grow, then it is increasingly important to have a fast network in place to handle the number of SAN backups occurring daily.

Large Servers: In some cases, a SAN backup may turn out to be slower than using a tape backup when the data sizes are extremely large. For this reason, many backup storage architectures incorporate using dedicated tape devices that are kept local to these larger servers to reduce the strain on the SAN network.

Data Recovery Times: Restoring data across a network is always going to be constrained by the IO bandwidth of the network. With SAN backups, the fastest data recovery times are achieved using a SAN bootup approach.

However, for disaster recovery of an entire IT system (possibly dozens of servers) the network speed will add additional time to the restoration process. These data transfer times will be worsened if restoring data from a remote server over FCIP, and will prove impossible if all external connectivity is gone (e.g. due to adverse weather, power spikes, etc.).

Most storage administrators factor this into their SAN backup solutions by incorporating a local SAN tape backup of critical systems. The business continuance timelines (how quickly core systems can be restored following a catastrophic event) should be set out in the firm’s disaster recovery plan, and these will dictate the amount of onsite/offsite backup storage redundancy that is needed.

Related Articles:
- Our post on how to choose the best backup solution differentiates between HDD/DVD/online backup solutions in more detail.
- The evolution of website backup approaches, software, scripts and technologies.

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