In Exchange Server 2010 it is possible to create a Database Availability Group (DAG) where the nodes contain multiple server roles. For example, you can create a 2 node DAG where each node contains the Hub Transport, Client Access Server and Mailbox Server roles.
In Exchange Server 2010, all messages are routed through a Hub Transport Server in the Active Directory site. The Hub Transport Server keeps a shadow copy of the message (when supported by the receiving server of course) and the message is temporarily stored in the transport dumpster. When a mailbox fail-over takes place, the Mailbox Server will request the Hub Transport Server to retransmit the last messages to prevent any data from being lost during the mailbox fail-over.
A few months back I wrote an article titled “7 reasons why High Availability will help you fail in even more spectacular ways than ever!” It was a humorous but legitimate look at some pitfalls you might face when implementing highly available systems (e.g. clustered servers, failover firewalls and etc.). However, after finishing that article I felt I hadn’t quite addressed the issue in toto. Then it struck me. The previous article focused mostly on the hardware and technology, but paid scant attention to the technologists working the hardware, and the more personal assumptions that can be made when considering and implementing highly available systems.
I was on a long haul international flight a few days ago, trying to endure 14 hours in a metal tube. As my troubleshooting mind usually does, it was thinking of ways to make the flight more comfortable and efficient. I had all kinds of wonderfully impractical ideas about ways to speed up baggage collection and deal with the poor sucker in the window seat needing to use the lavatory with two sleeping people blocking the path.
If ever there was a universal tincture in the realm of Information Technology, it would have to be the boot disc (followed closely by the prybar, but I’ll save that discussion for the next episode). The popularity of boot discs seemed to explode in the mid-2000s, with a disc for just about any situation you could find yourself in. Many a SysAdmin has saved their retirement plan from a hasty rollover action with the aid of a well-chosen boot disc. The love affair between SysAdmins and their boot discs is still going strong, of course, and with good reason – they are phenomenally handy things to have to hand. With that in mind, here are ten of the most useful boot discs you can have ready for action, which will help propel you into the quixotic realm of SysAdmins who are not chemically dependent on antacids:
