Areca always provided Linux drivers for there PCI-X/PCI-Xpress RAID cards. However I just noticed Andrew Morton implemented these drivers in his -mm tree, which makes implementation in the default Linux tree a lot closer. The first release of Andrew's -mm tree with the Areca driver inside is 2.6.11-rc3-mm1

It looks like the drivers are based on 1.20.00.05, which is peculair as these are not yet released (last version 10.20.00.04) by Areca (atleast the Areca FTP site hasn't got them). The changelog of 2.6.11-mm2 also indicates some fixes and that their is a lot of work needed to fix up these driver to 2.6 standards. 2.6.11-rc3-mm1 still has the 1.20.00.04 version of the Areca driver.

There is a little patch by Andrew Morton to make the Areca driver compile everywhere (kernel source does not have to be in /usr/src/linux). However this one is present in 2.6.11-mm2.
Also present in 2.6.11-mm2 is an patch from Adrian Bunk which does some general clean-ups to the Areca driver.

The main differences between the 1.20.00.04 and 1.20.00.05 seem to be big cleanups off the code to make it work better on 2.6 and rely less on own code to do things but to offhand this to code already present in the kernel. This already reduces the source code of the driver with a whopping 40 kbyte. In practice it would result in a more stable driver. But that's something we still have to find out.

Tomorrow I'll test run 2.6.11-mm2 on Stefan's box which has an Areca ARC-1110. I'll test basic performance and the workings of the Areca CLI tool.

UPDATE: The driver works without hassle on the box, however the CLI unreliability has not been fixed. Sometimes the Areca CLI refuses to work, but if you invoke it again it will work. This behaviour is not deadly, but very irritating if you are using the CLI for automated purposes (like nagios monitoring). However I would everybody recommend using the -mm tree if you are using an Areca RAID controller as positive feedback on this driver will speed up it's default implementation in the 2.6 kernel tree.