--On Saturday, August 13, 2011 08:59:30 AM -0400 William Warren hescominsoon@emmanuelcomputerconsulting.com wrote:

On 8/13/2011 7:40 AM, B.J. McClure wrote:

...

boot partition must be raid 1. Grub does not work with 5, 10. etc.

found out grub will not boot directly off the /boot md device..but i can make grub put itself on the mbr's of both disks..:)

Both steps are necessary for a properly redundant configuration. Depending on the age/interface/BIOS of your machine, if you lose your primary/master hard disk you may have to switch cabling to make your other disk (containing the mirror of /boot) the primary/master. Many modern BIOSes will allow you to select the boot priority order between disks without moving cables.

This is something that is best determined empirically before you put your machine into production ...

Typically, I do the following: 1. Put /boot onto a mirrored md device based on 200MB partitions. 2. Put the remaining disk space into a second partition using whatever RAID level is appropriate (including 5 or 6) 3. Give the large raid device to LVM 4. Add LVM-based filesystems as necessary. 5. After the system is fully installed, ensure that all boot drives have a copy of the proper MBR. 6. Test by powering down, removing the original boot drive, and powering up again (after ensuring that all RAID sync operations have been completed).

This has worked fine for quite a while (CentOS 5.x) and I can verify that RAID1 (/boot) + RAID6 (remainder) work just fine with CentOS 6, including putting an encryption layer between the RAID6 device and LVM.

Devin