Data Safety

Online storage is in constant use in the data center performing real-time data transactions for server applications. Online data storage protection consists of disk drive-based storage, sanpshot and replication

A disk subsystem that is used to increase performance or provide fault tolerance or both. RAID uses two or more ordinary hard disks and a RAID disk controller. In the past, RAID has also been implemented via software only. Various configurations of RAID levels are available i.e. RAID 0, 1, 2, 3, 4, 5, 6, 0+1, 5+6, 10. 

Taking a “snapshot” backup of your data is the easiest way to perform a remote replication. After a snapshot is taken, the incremental changes are sent to the remote site. There is a tradeoff between frequency and bandwidth. Data rewritten multiple times between snapshots is transmitted only once with the final data. Typically snapshots are taken several times per day. Databases need to be quiesced momentarily during the snapshot and special database agents are provided for applications like Oracle and Microsoft Exchange. This solution is best for recovering from a local disaster with loss of only a fraction of a day’s work.

The replication strategy depends on the data to be backed up. The more valuable the data and the more irreplaceable, the more frequent the replication. There are two types of replication synchronous and asynchronous. Synchronous replication over IP networks would entail unacceptable delays in the execution of the primary application and is limited to networks with private leased lines and large financial transactions. Asynchronous replication queues up the data and transmits it, as bandwidth is available. It is by far the most practical for the vast majority of applications. There are two popular types of backups that are replicated via asynchronous replication below.