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#6 Re: Software RAID5 and LVM with the Etch Installer Posted by cef (59.167.xx.xx) on Sat 24 Mar 2007 at 01:20 The perc2 is SCSI, yes? That really does look like some sort of software issue, or possibly a management issue on the controller (not allowing you to boot off multiple drives, not detecting drives with ID's higher than the dead one, etc). Unfortunatley on the management side, there isn't much you can do to get around it. If it kept failing to see drives past the dead one, admittedly you could pull out the cable on the dead one and hopefully things should be fine. If you were using Parallel ATA drives (standard IDE), then the following might apply: Using master/slave combinations in a RAID array is not a good idea. If the electronics of a PATA drive goes, it can take out the IDE bus, as unlike SCSI, they really weren't designed for hot-swapping, as the electronics (mostly) can't handle it. In the case of a master, this may stop the slave from being seen, meaning that the failure of a master drive causes the failure of two of the drives in your array, instead of just one. RAID 5 can only recover from one dead drive, so it's a bit of a problem. All of the hardware raid controllers I have seen for Parallel ATA drives have 4 (or more) seperate controllers on board, every drive gets it's own cable and you run the drives in master mode. By going down the master/slave path, you lose such protection, so don't complain if it fails! Great for testing RAID code if you're a kernel hacker, but not useful for anything remotely resembling production. Serial ATA doesn't suffer from these problems, as you don't daisy-chain the devices. On the software side I do know that the raid tools have changed a bit, so your problems might have been caused by that end. Also: Did you actually create a config file for mdadm that contained all the raid details? I've found the autodetect stuff (which is in the kernel) is not as reliable as it could be, so following that up with explicit definitions of what should be where seemed to help me in most of my situations. Most of the new installer stuff does that for you, so this only applies to older installs or manually created arrays. PS: The hardware bit on PATA I gave for reference. I'm sure someone out there might find it useful. It was also predominantly typed in before I realised that the perc2 controller is SCSI. Rather than lose it, I simply edited it a bit.

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