High availability of databases for cloud

In current cyber age, almost all the services are being provided to users over the cloud. Many of these services need to be highly available. Since these services require databases, the databases themselves must be made highly available. Redundancy is the technique of doing this. For this purpose Remus and its adaptation RemusDB use complete virtual machine migration to a backup host which is completely transparent to DBMS.

This approach incurs a lot of overhead as the amount of data transferred to the backup host is large and this transfer is done very frequently. Another system Postgres-R works only with PostgreSQL databases. This system replicates data without taking into account the number of requests for a particular table and the load on the servers. In this paper we proposed a solution which is based on another existing system Threshold Based File Replication (TBFR) and uses the current system load to achieve load distribution.