[NBLUG/talk] More questions about RAID

[Walter Hansen]

As I remember you partition the one drive and then partition the other 
drive to match. Then you link the individual partitions to create md0, 
md1, etc. At that point the raid will start building the mirror on the 
other drive. I don't remember if you have to format the other partitions 
or not, but I don't think it would hurt. File systems should be the same 
type on both drives. It's sorta pointless to raid the swap, so I usually 
make two swap partitions (non raided) one on each drive.

After a meeting a couple weeks ago I would recommend NOT having matched 
drives. The thing is matched drives tend to die about the same time. It 
would be a better approach to get two similar drives (perhaps different 
manufactures) of the same size.

Another thing is testing the setup. I did a test and found that I could 
not boot off driveB when driveA was missing but the other way worked 
fine. I had to do some work with lilo to make it boot ether way. This is 
not the biggest issue, but if you want real time redundancy it is an issue.

There is no difference between a raided partition and a non raided 
partition. You can take down the raid and use ether one of the drives 
normally, bring them up on another system, etc.

That's the problem with these multi drive USB drives. They use their own 
raid (non redundant) system. If one drive fails all the data is useless. 
They are twice as likely to fail.
Jack Smith wrote:
> I'll be using software RAID on Fedora 8, RAID 1
> 
> I have two identical hard drives.  One is partitioned for root, boot, and
> home; with some left over, unused.  The other is still uninitialized.
> 
> Are RAID arrays set up on a partition-by-partition basis?  Would I have
> three separate RAID devices, md0, md1, and md2?
> 
> Do I partition the second disk before I start?
> 
> Is mdadm somehow smart enough to mirror the sda data to sdb or is there a
> chance that I'll mirror the blank disk on to the first?
> 
> Thanks,
> 
> 
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