[CentOS] Re: Software RAID: on same IDE port or on different ones?

Scott Silva ssilva at sgvwater.com
Thu Oct 18 23:05:09 UTC 2007

on 10/18/2007 3:54 PM Kai Schaetzl spake the following:
> Scott Silva wrote on Thu, 18 Oct 2007 12:51:38 -0700:
>> The speed issue is not the problem. The problem is that if one disk dies while 
>> the system is running, it usually locks up the ide channel until a reboot, so 
>> the other drive would also be locked.
> Ah, I see, that makes sense.
> That sort of kills one of the reasons 
>> for raid. You can pick up PCI IDE cards cheap, put the drives on their own ports.
> Well, there are two ports on the board. But room in the 1U boxes is scarce, so I
> started out by just adding another disk and refrained from dragging another IDE 
> cable thru the holes inside the box. 
> Well, I have already two with this master/slave setup. Documentation says that 
> mdadm.conf holds all the information, but it doesn't specify any harddisk devices. 
> Are the UUIDs really all it needs to reassemble the array? So, it doesn't matter 
> (for RAID) that the drive moves from hdb to hdc?
> Kai
As long as the partitions were raid-autostart (fd I believe) it should pick it up.
Having a CDrom on a channel shouldn't be a problem as long as the drive 
supports UDMA, which I think the modern drives support.
And losing the CD along with the failed drive is not a big deal.

You still need to reboot to replace the failed drive, but the system should 
run until you get there. Think about also putting your swap on raid if the box 
swaps occasionally.

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