Why Dropbox was Unstable This Weekend?

Users of Dropbox had difficulty accessing the file storage service in the last weekend. The Dropbox website went off the air late on Friday (10) and remained unstable for more than 24 hours. On Sunday (12), the company said that the problem was caused by routine maintenance, but gave no further details. Now Dropbox explained how it happened.

Dropbox denied speculation that the service had suffered an invasion or DDoS attack. The problem was caused during a scheduled maintenance for Friday afternoon (10), which aimed to upgrade the operating system of some servers Dropbox. A bug in the update script made “a small number of machines” have the operating system reinstalled.
The company said it “uses thousands of databases” to make the service work and said that each of these banks have a primary and two secondary machine for redundancy. If the primary fails, there are two to keep the service in the air. Before you upgrade, the script verifies that the data are being used, but a bug allowed the operating system reinstallation active machines, which held the service in the air, which caused the fall of the site.
To put the site up as soon as possible, Dropbox claims to have restored database backups and managed to return with most of the functionality within three hours, but some larger databases took longer to be imported, which caused problems in some functions. Who accessed Dropbox this weekend realized that the Photos tab, which displays the latest images sent by mobile phone or computer was inaccessible.
Despite the need to restore backups, which are stored in a separate environment from production servers, Dropbox claims that users’ data “were never at risk during the interruption.” This is because these databases have no file information: they are only used to provide album sharing features, automatic sending of photos and API functions.
Dropbox apologized to users. The company said it added a verification step to prevent a bug as it affects servers in the future. Furthermore, Dropbox said to have developed a tool for making faster restoration MySQL databases, allowing the site becomes less time outside air if a problem similar to happen, since the pattern is slowly tool to restore bulk data. It is planned, according to Dropbox, open-source tool.