It depends on what you're trying to do. Does the business application require very fast recovery (RTO = 0) or zero data loss (RPO = 0)? Or both? It also depends on what kinds of loss or damage you need to recover from. Do you ever need to restore individual files? Does the application span multiple disk volumes? The right solution will depend on the application, the business needs, and the existing infrastructure capabilities.
Recovery solutions may protect data at the application, file system or logical volume level. For example, synchronous disk mirroring can speed recovery from hardware failure or site outage, but will not protect data from accidental deletion or malicious damage. Frequent snapshots can enable recovery to a known good state of the data, but some recent transactions may be lost in the process. A journaling file system or database log file can assist recovery while also preventing or minimizing data loss. Some virtual disk architectures provide rollback capabilities at the logical volume level.
Some of these solutions work for recovering entire volumes but not for restoring individual files -- or for recovering databases that span multiple volumes. So you may need multiple, complementary capabilities to meet the full range of business requirements.
These choices have implications for archiving and compliance, in addition to backup and recovery. Disk-based archives can provide important business and compliance benefits, compared with tape-only archives. Disk-based archives enable faster response to inquiries from regulators like the SEC, and also less costly/more timely response to litigation discovery requests. They can also enable faster response to customer inquiries and internal audit requests. In most cases, disk-based archives should be backed up to tape media -- so you still don't get to eliminate tape!Ed note: If you would like to read additional compliance articles, opinions and expert advice, make sure to sign-up for our ALERTS on compliance. Click here to sign up. SearchStorage.com also offers alerts on low-cost storage.
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This was first published in November 2003