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File systems

The inclusion of Ceph and LogFS in 2.6.34 further expands the number of file systems supported by the Linux kernel. Ceph is an experimental, distributed, replicating network file system for clusters licensed under the LGPL. According to the developers, it is suitable for managing data volumes in the petabyte range "and beyond", is already pretty stable, and offers numerous features missing from comparable open source file systems. Kernel Log Logo Although it uses parts of the still experimental Btrfs file system code for storing data, Ceph, should already be usable – though the developers do strongly advise users to back up important data.

LogFS uses log structures and is of primary interest for flash drives with no wear levelling as used in embedded systems. Roughly speaking, the file system does exactly what the firmware for solid state disks (SSDs) with SATA connectors does.

Btrfs maintainer Chris Mason briefly elucidates some of the major changes in Btrfs in his git pull request. Various changes aimed at adding support for LZMA compression to SquashFS (used for Live CDs) proved not to be to Torvalds' taste. They will now be rewritten, but this could take some time. A change to the partitioning code should allow the Linux kernel to work with hard drives with both a physical and logical 4 KB sector size. According to both commit comments and a recent discussion on LKML, Western Digital is planning to introduce just such a hard drive in order to get around the 2 terabyte partition limit on hard drives partitioned using MBR.


Networking

Downloading the Linux kernel

New versions of Linux can be obtained from the Kernel.org servers; the contents of these servers are also mirrored on numerous mirrors internationally. However, Linux users who are not familiar with the details of the kernel and its environment should generally not install new Linux drivers and kernels themselves but use the kernels provided by the Linux distributors instead.

The network subsystem gained various new Ethernet drivers: qlcnic, greth, ksz884x, smsc75xx and cxgb4 (1, 2). Also new is the ixgbevf driver (for example 1, 2/documentation), which by use of SR-IOV allows guest systems to communicate with other systems via the virtual networking features offered by Intel's 82599 family of 10 Gigabit Ethernet controllers – for this purpose, the ixgbe driver, which supports these chips on the host system, was extended to support SR-IOV (1, 2, 3).

Further additions to the kernel include vhost-net, which is designed to increase performance in virtualisation solutions such as KVM or Lguest – vhost-net is a kernel-internal server for the Virtio framework outlined in the commit comment which operates in the kernel and is designed to reduce overheads when guest systems use virtual Virtio network hardware to exchange data with operating systems that run on different hardware.

The new macvtap driver offers more flexible and faster network data exchange facilities between the guest systems on a host as well as various other options. The developers are preparing numerous other improvements for this driver and the Virtio server so that in the long term these components' performance and range of features will be further increased.

PCI and power management

Following Torvald's rejection of asynchronous suspend and resume patches in 2.6.33, he has now merged a revised version into 2.6.34 without fuss. These patches cause the kernel to suspend certain system components in parallel and wake them simultaneously. This should reduce sleep and wake times when using ACPI S3 / suspend-to-ram and hibernate / suspend-to-disk modes.

The kernel has previously offered only rudimentary support for utilising power saving technologies on I/O devices at runtime. In Linux 2.6.34 this has been significantly revamped and expanded (e. g. 1, 2, 3). The code which performs this task, which has long been in the USB subsystem, now makes use of the new generic functions. The new energy saving functions are, however, deactivated by default.

Next: Drivers: Audio, Input devices, Notebooks, USB and staging

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