Performance, performance, performance; this is what we hear in all software development and management sessions. ZFS provides few utility commands to monitor one or more pools’ performance. You should remember that we used fsstat command to monitor the UFS performance metrics. We can use iostat subcommand of the zpool command to monitor the performance metrics of ZFS pools. The iostat subcommand provides some options and arguments which we can see in its syntax shown below: 1 iostat \[-v\] \[pool\] .

Like other operating system we can assign multiple IP address to a network interface. This secondary address are called logical interfaces and we can use them to make one machine with one single network interface own multiple IP addresses for different purposes. We may need to assign multiple IP address to an interface to make it available to both internal and external networks or for testing purposes. We should have one network interface configured in our system in order to create additional logical interfaces.

Link aggregation or commonly known Ethernet bonding allows us to enhance the network availability and performance by combining multiple network interfaces together and form an aggregation of those interface_names which act as a single network interface with greatly enhanced availability and performance. When we aggregate two or more network interfaces, we are forming a new network interface on top of those physical interfaces combined in the link layer. We need to have at least two network interfaces in our machine to create a link aggregation.

In this part we will look at how the directory tree walker and the directory stream reader works. These two features are another couple of long requested features which was not included in the core java before Java 7. First, lets see what directory stream reader is, this API allows us to filter content of a directory on the file system and extract the file names that matches our filter criteria.

For long time Java developers used in-house developed solutions to monitor the file system for changes. Some developed general purpose libraries to ease the task of others who deal with the same requirement. Commercial and free/ open source libraries like http://jnotify.sourceforge.net/, http://jpathwatch.wordpress.com/ and http://www.teamdev.com/jxfilewatcher among others. Java 7 comes with NIO.2 or JSR 203 which provides native file system watch service. The watch service provided in Java 7 uses the underlying file system functionalities to watch the file system for changes, so if we are running on Windows, MacOS or Linux… we are sure that the watch service is not imposing polling overhead on our application because the underlying OS and file system provides the required functionalities to allow Java to register for receiving notification on file system changes.

What is a file system File systems make it possible to store and retrieve files and containing data into storages like hard disks, optical disks and other types of storages. OpenSolaris support both legacy file systems like UNIX File System (UFS) and its own file system called Zettabyte File System (ZFS). Following figure show how UFS and other legacy file systems work. As you can see we can partition each storage device into one or more volumes with different file systems.