Emergency measures for sudden power outage of network servers

I recently spent a few weeks in a small, remote village for a consulting project. Because calling home is very expensive, my wife and I contacted by email.

But after a few days after leaving the US, the power supply was suddenly interrupted. Although only one second, our computer could not access the Internet. In the end, I can only call 12,000 miles to request help.

Although all of our computers are connected by UPS, one of the UPSs did not work in time, so all servers connected to that UPS stopped working. These servers are configured to start up automatically when they are powered on, but my DNS server cannot be restarted due to a problem accessing the network. The problem will only be resolved if the DNS server is started manually.

What happens if your company loses power? In most cases, you will also connect all servers to the UPS, but you also see my situation, UPS will also fail, especially for a few years.

If you are experiencing a power outage and the server is down, you can solve the problem simply by starting the server after power is restored.

NTFS can protect you

A few years ago, I was an administrator on the NetWare network. Whenever there is a power outage, I usually have to recover it from a server backup that has stopped working.

But now, when there is a problem with a file or print server, we rarely use this method again. Many people don't realize it, but the NT File System (NTFS) does include protection against power outages. Only when a file is created or modified, NTFS recognizes the operation as a handler. This means that the transaction log has been written before the operation is written to disk. In fact, any time you want to write a file to an NTFS, Windows will do the following:

Record the processed meta-data operations in the RAM log file.
Record the actual meta-data operation in RAM.
Mark this process in the log.
Dump the log to your hard drive.
Write the actual meta-data operation on the hard disk.
(Note: The fourth and fifth steps do not always occur immediately.)
As long as these steps are performed, in the event of a power outage, Windows will automatically run CHKDSK as part of the boot. CHKDSK compares log files to hard disks. If there is a processing in the log file, and the processing is not in the hard disk or incomplete, Windows will use the information in the log to reconstruct and update the hard disk. The only data that is lost -- usually very small -- is the one that writes to the RAM log but does not dump the log files to the hard disk.

Reconnecting a document server to a web is relatively simple, but the application server needs more work. After the power outage, I started an application server and had to start some services manually, but otherwise, the server was fine. However, in many cases, if an application relies on a database, a power outage will destroy the database.

Exchange Server is an application server that relies on databases. It uses transaction logs in a way similar to the NT documentation system. Still, some data is lost when the power is turned off. If this happens, the database is in a conflicting state when the server is restarted. At that time you have to use some built-in maintenance tools to restore the coordination of the database before assembling the database.

There are many types of applications that rely on databases. Some applications use a transaction log for the database, and some do not. If your database server is powered off and it is not protected with a transaction log, you have to recover from the backup.