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The Linux community has been beavering away in the past few weeks in preparation for the 3.9 release of the open source operating system kernel. On April 29th the new kernel arrived, just a few days late, and brought with it a plethora of new features of interest to those running Linux servers.
We’re going to highlight a few of the best for you, so you don’t have to go digging through the release notes.
While there have been kernel patches for using SSDs as a cache for slower drives in the past, the new dm-cache functionality adds experimental support within the main kernel for using SSDs as a cache target.
Using the faster solid state drives as a cache for slower spinning disks can potentially speed up IO on servers considerably, while mitigating the need to spend big on outfitting an entire server with SSDs. The faster drives can handle reads and writes for data that’s currently in use and write changes back to the larger drives when convenient.
Btrfs, which already had native support for RAID 0 and 1, now adds RAID 5 and 6 to its capabilities. RAID 5 is popular because it has a low cost of redundancy when compared to other RAID methods. RAID 6 adds an additional parity block to RAID 5.
In addition to Btrfs improvements, the ext4 filesystem has been given some some attention, including the fixing of a performance issue in the journalling layer.
Multiple Sockets On One Port
With this addition, a Google developer has implemented the ability for multiple UDP or TCP sockets to be opened on one port. This means that, for example, several web server’s processes can open their own sockets on port 80. Processing load can then be evenly spread across the processes, improving load distribution across cores and preventing processor bottlenecks in servers.
ARM Support For KVM
Until this release, the kernel’s built in virtualization system didn’t work with ARM chips. The upgrade brings support for ARM’s virtualization features on Cortex A15 chips.
As always, there are many tweaks and improvements across all of the kernel’s subsystems, including better support for Intel’s forthcoming Haswell architecture, a new lighter sleep mode, improvements to the NVIDIA graphics drivers, including the addition of support for Optimus devices.