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Libguestfs 1.14 Rolls Out

New tools help users analyze and fix alignment problems in guests.

In a blog post today, Richard Jones, Senior Software Engineer at Red Hat, announced the release of libguestfs 1.14, an open source set of tools for accessing and modifying virtual machine (VM) disk images. "I'm really charged about how the new tools let you analyze and fix alignment problems in your guests," Jones tells NetworkWorld.

"This is a big — and probably under-appreciated problem," Jones explains. He says virtual machines traditionally aligned their partitions to odd sector boundaries, and sector 63 was very popular. "Network storage and some new hard drives work with 4K sectors. Mapping unaligned 512-byte sectors in the guest down to 4K sectors in the host can sometimes cause twice the amount of I/O to be performed, resulting in serious performance penalties," he says.

Jones says they worked to fix the performance issues in two ways. First, you can analyze whether your guests have a problem using the this new tool with the virt-alignment-scan. Second, users can fix the problem for many guest types, including all Windows and many Linux guests, using enhancements to virt-resize. "virt-resize is now a very comprehensive tool for resizing and aligning your guests," he says.

The release notes thank Erik Nolte, Senior Network Engineer at Beyond Oblivion, because ArchLinux support now works with Linux 3.0. No security problems were found or fixed in this release, according to the notes. Many bugs were unofficially fixed, and 18 bugs were fixed officially. The new release will be the basis for libguestfs in Red Hat Enterprise Linux 6.3.

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