[clue-tech] SCSI RAID to Software mdadm

[mike havlicek]

Hello,

I have what I call a funny box. Its an old HP pavillion desktop system
where using a drill and screws, and such I have modified the drive cage
to hold 3 u320 drives controlled by an inferior RAID controller (mylex dac960 type card). Its probably no longer eligable for HP support... After about ten months of service the RAID 5 got flakey reporting a particular drive dead repeatedly. I believe I have read that this particular card is notorious for this kind of behavior when in fact the physical hard disk is OK. The quota of rebuilds was evidently exhausted for the array configuration.... I have wiped the configuration and rebuilt the system drive; restored the OS environment (CentOS 5.X) from backup. It has been booting successfully without the controller barking about critical or dead compononents for all of the handfull of reboots since rebuild.

Looking forward I am thinking about replacing the mylex controller card with an adaptec array controller that is only supported as a SCSI controller (no hw RAID) in linux. (This is all based on th constraint of what spare parts I have laying around). 

I want to mimic the disk structure that is currently running with HW raid in software. Currently the 3 disks are configured in a RAID V. From linux there are 2 partions on the system disk, a native linux used for /boot
and an LVM type for everything else (grub on MBR). IE I am considering trying to put as much of the system as possible in LVM living on top of a software RAID V. 

Based upon the centOS installer not allowing you to put /boot in the
LVM last I checked, I assume that /boot still cannot be a logical
volume with lvm2. (?) Lower than that I initially was thinking
that /boot needed to be separate from the md device(s) but I am now
questioning that. My first thought was to make a primary partition for
/boot on each of the three drives keep them somewhat synced with whatever
necessary drive reference differences accounted for in the grubbing process. This seems a bit cumbersome but less irritating than what the
HW controller was doing. 

After all of that I guess I am only about 89% confident and 100% too
lazy to search for/through/man the mdadm strapping process to confirm
that at a minimum/best the system can have all but /boot living on LVM
on top of mdadm software raid using grub.(?)

Actually I just thought I would ask prior doing the document investigation
that I should do anyway before proceding.

Thanks,

-Mike