Backup and Replication – Why Replication Isn’t Enough
We frequently talk to customers about their backup and disaster recovery plans. A topic that often comes up is that the customer feels they are covered by their replication of data and don’t need to have a separate backup schema.
Let’s analyze that: The replication system will typically create a real time copy of the data to a secondary, possibly remote, site. Everything that is written to one storage system is replicated to the other. It’s pretty simple, and, if you have enough bandwidth between the site, very attractive. It can do a good job of protecting from site failure. If the storage systems include something like the Compellent Live Volume feature, you can have very fast recovery between sites.
But that doesn’t protect against what I call a “Layer 8” failure; the incredible ability we humans have to make a mistake. For instance: Bob decides he no longer needs a file and inadvertently removes the directory. Replication will immediately make the change to the remote site too. You no longer have any copy of the directory on either system.
Some customers have snapshots implemented. They can help if you can go back into one of the snapshots and retrieve the directory, but the snapshot has to be replicated to the remote site also for it to be recoverable in a DR scenario. The snapshots also have to be available for the time the error occurred. Most snapshot implementations only have a few days of snapshots online, if that many.
A backup that is constantly doing small incremental backups will usually have that data on it. It is a simple matter to recover the directory to its original location. A replicated backup will also provide recovery at the remote site if the primary site is unavailable. A typical backup/recovery system will have several months of backups available, so if Bob deletes a directory or file and doesn’t realize it for several weeks, he can probably get it back.
While we are talking about site failures, it is critical that your backups not be stored on your primary storage system. If you lose the system, you lose your backup data and the ability to recover it. If you are not using tape or replication of your backups, you could lose your complete company. Abtech recommends a separate backup server/appliance for your backups, especially if you want to eliminate tape from your backup process.
Give us a call for help with all of your backup and disaster recovery needs.
Robby Wright, Chief Architect & Consultant