10-02-13 | Blog Post

SAN-to-SAN Replication: Fast Data Backup for the Private Cloud

Blog Posts

Need fast data backup with no impact on the performance of your systems? Read on about SAN-to-SAN replication as a reliable, synchronized method for data backup. This excerpt is taken from our Disaster Recovery white paper; full version available for download now.

5.4. SAN-to-SAN Replication

SAN (Storage Area Network)
Due to compliance reasons or due diligence, many companies not only want a backup locally that they can recover to very quickly, but they also need to get that data offsite in the event that they experience a site failure. SAN can help with these backup and recovery needs.

SAN Snapshots
A snapshot is a point-in-time reference of data that you can schedule after your database dumps and transaction logs have finished running. A SAN snapshot gives you a virtual copy/image of what your database volumes, devices or systems look like at a given time. If you have an entire server failure, you can very quickly spin up a server, install SQL or do a bare metal restore, then import all of your data and get your database server back online.

SAN-to-SAN Replication
The counterpart to SAN snapshots is SAN-to-SAN replication (or synchronization). With replication, if you had a SAN in one data center, you can send data to another SAN in a different data center location. You can back up very large volumes of data very quickly using SAN technology, and you can also transfer that data to a secondary location independently of your SAN snapshot schedule.

This is more efficient because traditional backup windows can take a very long time and impact the performance of your system. By keeping it all on the SAN, it allows backups to be done very fast, and the data copy can be done in the background so it’s not impacting the performance of your systems.

You can configure and maintain snapshots on both your primary and disaster recovery sites, i.e., you can keep seven days’ worth of snapshots on your primary site, and you can keep seven days of replication on your disaster recovery site.

However, SANs are fairly expensive, and snapshots and replication can use a lot of space. You will also need specialized staff to configure and manage SAN operations.

SAN-based recovery focuses on large volumes of data, and it is more difficult to recover individual files. Traditional recovery focuses on critical business files for more granular recovery, but that comes at the cost of speed. With a large volume of data, traditional recovery can be much slower than SAN-based snapshots.

SAN-to-SAN replication can support data security in a private cloud environment and provide fast recovery times (RTO of 1 hour and RPO of minutes). After a disaster is mitigated, SAN-to-SAN replication provides a smooth failback from the secondary site to the production site by reversing the replication process.

SAN vs. Traditional Backup and Disaster Recovery
Traditionally, 10 or 15 years ago, people had email servers, FTP/document servers, unstructured data and database servers. The backup and recovery of these systems must be viewed differently as they each present their own unique challenges.

With email servers, they are mission critical, highly transactional and essential to a business. They may have SQL or custom databases, and they can take a long time to rebuild after a disaster. The actual install and configuration of the application that sits on top of the database itself can be very intensive, and rebuilding that system may put you over your recovery time objective (RTO).

For a smaller company, an exchange server may be 100 to 200 GB in size. FTP/file servers can be terabytes in size, and contain large volumes of unstructured data. They are less transactional than email servers, and server configuration could be minimal. Each individual file must be backed up. When looking at systems of that size, you should stop looking at traditional backups, and you can start leveraging SAN (Storage Area Network) technology – which is a large group of disks.

Instead of having a backup window that runs for an entire day that can slow operations, you can use a SAN snapshot technology which allows you to back up more efficiently. If you need a backup of your FTP/file servers every night, you can leverage a snapshot during off-hours very quickly, from a matter of seconds to a minute. SAN snapshots can back up a large amount of data with very little impact on your production environment.

The tradeoff is it can be slightly harder to restore the data because you would need to bring up your file drive online and present it to the server. However, it can be faster than having to restore terabytes of data from a tape backup.

For standalone database servers with a large volume of structured data that are highly transactional, consider using SAN snapshot technologies with specified volumes for database dumps and transaction logs.

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