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Old 6th June 2006, 07:11
fraginhell fraginhell is offline
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Hi Steve,

I found a really good document on tripwire from one of the original redhat 9 manuals, which are still there, it has a section on tripwire, which is what I use, its great and takes you step by step on getting tripwire going.I have boxes with both software and hardware raid.
For Hardware RAID where the BIOS takes care of the mirroring the problem is the os will see the same disk twice, for example /dev/hda and /dev/hdc, well its seeing the two individual disks, but they look the same. The way round this is to build the system first on a single disk, add noprobe=/dev/hdc (this might need checking now its been a long time since I did it this way) to the boot looder kernel paramater to exclude the second disk and then add the second disk to the system. The O/S will totally ignore it. The problem is if you loose a disk you will need to move the second disk to the master location and reboot for the system to work, I've not found away round this problem, so I mainly use software raid, which seams to work fine and on my limited systems has no performance problems, and will handle a drive failure without crashing etc.
As for the RAID I think it mainly depends on your BIOS. For software RAID. I have for example each disk as the master on each controller (to stripe accross the controllers as well for performance and redundancy) so the os see's /dev/hda (-first disk first controller) and /dev/hdc (first disk on the second controller) if you have SATA disks then I would expect them to be /dev/sda etc etc, the O/S then seans /dev/md0 which is a logical reference to both disks, so for example /dev/hda1 (partition1 for example here) and /dev/hdc1 = /dev/md0

Disk Failure is fairly easy, you first replace the disk of course, and then replace the disk partitioning infomation so that your new disk contains the same partitions as the old one, finally re-sync the disks.
The only think I've not played with much is logical volumes and RAID, its possible and I've kinda managed once, but was difficult to setup.
I have played with RAID stuff quite a bit, pulling disks out on the fly and trying to replace them etc etc and it seams to work well.
Hope this all makes sense let me know how you get on.

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