Microsoft's Hotmail web-based email service is supposed to reveal a number of new features at a press event in early October. But before that event happens, Microsoft decided to reveal a new way that it is handling the data storage on Hotmail. In a new entry on the Windows Live blog site, Microsoft's Kristof Roomp talks about its upcoming storage improvements that will be put in place later this fall.
Just in case you might be wondering about Hotmail's stats, Roomp says, "Hotmail’s storage system supports over one billion mailboxes and hundreds of petabytes of data (one petabyte is a million gigabytes, or a million billion bytes). The system services hundreds of thousands of simultaneous transactions from across the world." Microsoft has been using a RAID set up for the Hotmail storage system for while. For those who are not familiar with the term, A RAID (Redundant Array of Inexpensive Disks) system basically links up two or more hard drives to one controller board. To the operating system, multiple drives under a RAID set up look like one big hard drive.
Roomp says that kind of storage system works if just one of the drives fails but " ... they don’t help if the whole machine or the RAID controller runs into problems. For larger drives, we found that having completely independent copies (on hard drives not sharing the same machine or controller) was much more reliable than a significantly more expensive RAID configuration."
The new Hotmail storage system is name JBOD (Just a Bunch Of Disks). In essence, the hard drives, instead of being connected to one controller board, are handled in software. Roomp says, "The software we developed for the JBOD system monitors the hard drives schedules repair actions, detects failures, and diagnoses repairs. This software consists of a number of “watchdogs” that constantly monitor for certain types of failures. If the watchdog detects the failure that it is looking for, it raises an alert, which automatically triggers a repair process." About 30 million Hotmail users are already using the new system and 100 million more will be transferred in the next couple of months.
In addition, Hotmail will also add solid state drives to handle other functions. SSDs are much faster than normal hard drives but are also much more expensive. Roomp says the new Hotmail storage system will use SSDs to handle features like "the list of messages in your inbox, read/unread status of your messages, conversation threading, mobile phone synchronization etc." This kind of data normally takes most of a hard drives activity. With SSDs handling this data and normal hard drives handling the actual email storage Roomp says, " ... we are able to take advantage of the trend in larger and cheaper hard drives without making any sacrifices in the performance of our system."