Info for Raid users on FC2

[Lucas Harms]

Hey all,

 

Seems that there are a lot of posts flying around about raid problems under
FC2 and the 2.6 kernel.  If this is old info to you, please disregard.

 

Under kernel 2.4 raid controllers that were not true hardware controllers
used the ataraid device-mapper to map the drives to the raid array.  This
means most Promise controllers along with pretty much any motherboard raid
support.  Or you can put it this way: If you did not spend at least $500 on
your raid card then it is more than likely a software raid controller.  Not
a true hardware controller.  Any instructions you see using ataraid under
2.6 will not work with the vanilla kernels.

 

Kernel 2.6 has done away with the old ataraid in favor of a new universal
userspace device-mapper.  In order to get a software raid controller to
function under 2.6 you have to use this new device-mapper instead.  Problem
is that it is not completely in place.  For information on how to use the
mapper read the following links to get you started:

 

http://lkml.org/lkml/2003/12/29/99

 

http://forums.gentoo.org/viewtopic.php?t=128781
<http://forums.gentoo.org/viewtopic.php?t=128781&highlight=devicemapper+raid
> &highlight=devicemapper+raid

 

Those are the two best sources I've found thus far.  Feel free to add more
info if you have it.  The second of course it specific to Gentoo, but that
is just a matter of using yum instead of emerge and rc-update.

 

This info only applies if you are using the raid bios to setup the array.
When you use the raid bios, you must use the new device-mapper in order to
use the raid arrays.

 

My personal recommendation is that you use the software raid support built
into the linux kernel.  It is very easy to setup via disk druid.  There have
already been a few links posted for linux software raids.  One of those
links should get you set.  For mirrored raid 1 arrays, it performs at the
same speed as the raid controller bios (if not faster).  You can still use
your raid controller.  Just do not define the raid arrays under the
controller bios.

 

If you have to use the raid bios for whatever reason and cannot wait until
the 2.6 device-mapper support is complete, then use the links mentioned
above as a starting point.

 

Luke Harms

lharms at scenpro.com

 

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