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Until recently, the use of secondary storage in a backup context -- temporary storage of data from a backup prior to it being written to another storage medium or caching a copy of the data -- was an expensive luxury for all but the biggest of companies. But while computing environments and the data they generate and back up continue to grow, the same cannot be said of backup windows. As recovery time objectives and recovery point objectives decrease, the tolerance for any downtime or data loss continues to dwindle.
There are ways to make the backup process more efficient and even more useful using the advantages of secondary storage as a storage staging area.
Examples of secondary storage options
With the cost of disks falling and the need for more capacity skyrocketing, using a disk-to-disk-to-tape methodology is a good option. Depending on the requirements, a company may want to forgo the use of tape altogether -- it can be a slow and error-prone process -- and use remote disk-based backups for better speed and simplicity.
Streaming directly to tape is extremely inefficient in all but the smallest environments and can be costly in terms of the maintenance and manpower required to manage the storage medium. With the advantages of secondary storage, all sorts of disaster recovery (DR) capabilities open up as well. A few simple examples include:
- The capability to immediately restore a group of files from the latest backup after the tapes have been shipped off-site.
- The ability to replicate data to a DR site. A current copy of the data will help speed up service restoration.
At the same time, replication to cloud-based products is becoming an ever more popular solution. Backing up to secondary storage before writing to tape or uploading to the cloud provides several tangible advantages. For example, when there is a lot of data to be backed up, secondary storage enables the backup to run during the day, essentially expanding the backup window significantly.
Secondary storage leads to simpler recovery
A local copy on secondary storage can be restored in mere minutes, assuming fast disk access. There is no need to locate and load tape, load the software to locate the data and then restore that data from the tape. Thanks to the advantages of secondary storage, the restoration comes directly from the secondary storage rather than the tape. Tape access, on the other hand, can be slow and subject to loss or damage. In addition, encryption is built into the secondary storage at the disk firmware level, so physical data loss becomes less of an issue.
Depending on the secondary storage capacity, several days' worth of files are backed up while copies are safely stored at an off-site location.
Object storage is a good candidate for secondary storage, according to analyst Marc Staimer.
Use secondary storage for efficiency, but keep an eye on cost
Secondary storage enables an administrator to use other flexible backup options, such as snapshots. All major backup software players provide snapshot functionality, which provides a systemwide crash-consistent backup. Unlike traditional backups, the technology makes lost files, unticked file selection options or a changing file system into nonissues.
Advantages of secondary storage also include an increase in backup efficiency and a reduction in the duration the backups require. Overrunning backups are the bane of many an administrator, and remediation can be quite problematic during the working day.
Adding secondary storage can add cost to a setup due to the price of not only the physical disks, but the maintenance and support of that additional storage. However, at the same time, it introduces a huge amount of flexibility and operational capability to the administrator's virtual tool belt.
Secondary storage setup tips
Remember these important aspects when setting up so you can fully appreciate the advantages of secondary storage:
- If possible, keep the secondary storage infrastructure separate from the main infrastructure. Failure to do so could mean that, if there was a serious problem with the storage infrastructure -- be it hardware or some other type of outage -- the capability for a quick restore from secondary storage would be lost, and restoration could take a lot more time, requiring tapes and additional management complexity.
- The backup network and secondary storage network should be isolated. The backup infrastructure and production infrastructure shouldn't share any commonality. Not only does having a physically separate backup network keep the production network clear for production data, it also aids in keeping the backup infrastructure secure. Done badly, it can be impacted by cryptomalware or viruses. Network isolation, firewalls and strict access control should be used to help secure the environment.
- The administrator will need to think carefully about accurately sizing the secondary storage, its capability and its performance versus speed and cost tradeoffs.