Have you ever run out of disk space on your production server? Do you cringe at the downtime required to bring filesystems offline, backup, create bigger filesystems, and restore, all the while typing with crossed fingers? Do you dread deciding the disk layout for your new server? You do not need to panic! ZFS has you covered. In one simple command, you can add space to a ZFS pool without taking it offline.
Descendent (child) filesystems in ZFS take on the characteristics of the parent filesystem (compression, quotas, and available disk space). The pool concept in ZFS is fitting – a hard drive (or several) becomes a pool. We no longer have to define the exact size of a filesystem when we create it. Each filesystem has access to the same pool of space. However, it is simple to reserve a minimum amount of space for a filesystem and its decendents.
Creating new ZFS filesystems may seem strange at first since they are initially mounted under their parent filesystem. This is no problem since ZFS provides a simple and powerful mechanism for setting the mount point for a filesystem.
The distinction between ZFS pools and filesystems is worth repeating. A ZFS filesystem cannot exist outside of a ZFS pool. Creating a ZFS pool also creates a ZFS filesystem of the same name. Understanding the second part can help avoid confusion. This tech-recipe describes the simple step to list the ZFS filesystems configured on the system.
A previous tech-recipe demonstrated the command to create a ZFS pool using zpool. While this created a mounted filesystem, the fun does not stop there. The pool can be used in additional ways. This tech-recipe shows how to create more filesystems out of an existing pool.
Cygwin is a great tool for UNIX people stuck in a Windows world as it provides a vast assortment of UNIX tools in a Windows command prompt. One of the most powerful uses of Cygwin is as an X server. While it may be useful occasionally to run a single X application in its own window, that can be boring. As a more exciting option, it is simple (one command) to launch a full Solaris desktop session complete with login screen.
A JOIN is a way to connect related database tables by the common values between them. A left join contains all of the rows from the primary table plus related members of the second database if they exist. Using joins can significantly reduce the number of database queries required to render a web page. This Tech-Recipe describes how to do a left join in Symfony using Propel.
If you forget to carry your glasses, using your Windows Phone 8 with small text will be a problem. Luckily, you can use the magnifier to zoom the screen in and out to enlarge small text and make content clearer.
An array is one of the fundamentals of almost any programming language. Whether you understand what it is or you just need to learn the syntax, the process of creating arrays in PHP is relatively straightforward.
The mount and unmount commands are not used with ZFS filesystems. The filesystem concept has changed with ZFS in which we are likely to see many more filesystems created per host. A ZFS pool can be taken offline using the zpool command, and a ZFS filesystem can be unmounted using the zfs command as described in this tech-recipe.
Anyone who has used DiskSuite to mirror drives in Solaris knows that, while not difficult, the multiple steps involved are fertile ground for (potentially devastating) heartache. This is not the case with ZFS. Creating a mirrored pool with ZFS makes DiskSuite look like rocket surgery.
ZFS will change the way UNIX people think about filesystems. How do you use fsck with a ZFS filesystem? The answer is that you do not. ZFS filesystems are always clean, so even in the worst case of a power outage bringing a system down, you will never be asked to give the root password for system maintenance again. With ZFS, data are always consistent on disk. For you worriers, there is a command you can use to make sure everything is okay with your filesystems.
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