Cloud computing in the face of unexpected conditions are the advantages

System crash recovery is a daunting topic. But we have to face it again. Take a company's mail system as an example. Some companies back up used mail, either daily or weekly. However, after the tragedy, the backup data is restored to System, it can only be the day before or the previous week. This periodic backup only ensures the safety of the backed up data, but it can not be accurate to the previous use and takes a long time to recover. So, let me talk about the advantages of cloud computing it.

Larger companies may use SANs for backup, but SANs are expensive, and even the SAN is risky if the entire data center fails. So, those truly powerful big companies will create a new database offsite and create a complete backup system.

However, it is often unsatisfactory. Sometimes even two data centers in two locations will hang up at the same time. Therefore, a more powerful company will maximize the physical distance between the two data centers (the farther away The higher the cost, however, there are management issues that require terabytes of data to be transferred between two SANs and require very high bandwidth. In any case, these are cost-related, with more redundancy and higher costs .

There are two indicators of disaster recovery and recovery, one is RPO (Recovery Point Objective), one is RTO (Recovery Time Objective), which is the data loss rate and recovery interval. The traditional SAN or off-site backup, these two indicators depends on the cost, the better the indicator, the higher the cost, Google in this regard, using synchronous replication technology, synchronous replication RPO close to 0, and RTO near real-time, That is to say, at the time of the disaster, all online applications in Google lost almost zero data, and the recovery interval was close to real time, making the user completely unnoticed (however, how many times of Gmail's downtime - translator). Data sync replication technology is applied to all Google online applications (including Gmail, Google Calendar, Google Docs, Google Sites, etc.), and any data that users need to save is synced to data centers in two different geographies of Google, A data center failure, the system will immediately switch to another data center.

The cost of operating a synchronous replication backup is quite high. For commercial storage, the 25GB Synchronous Storage Service may require 150 to more than $ 500. Each year, Google guarantees that these high-cost technologies are available free of charge to users by:
1. One of Google's data centers supports millions of users, so the cost per user is relatively low.
2. Instead of enabling Google's backup data center at the time of a disaster, Google has always been using Google to balance those data centers and ensure no wasted resources.
3. Google's data centers have their own highly connected networks that ensure fast data transfer.

The advantages of cloud computing are the rapid adoption of advanced technologies, Google's cloud computing, cloud storage and other applications that make services that were previously only available to super-companies to become commonplace and at very low cost.