Stupid RAID question

[Lennart Sorensen]

On Mon, Oct 03, 2011 at 03:55:13PM -0400, Andrej Marjan wrote:
> I've been having rotten luck with reliability of 1TB drives, so I'm finally
> biting the bullet and trying to figure out RAID. So far I have a tenuous,
> but (seemingly) working grasp of how to make device mapper do RAID1 and how
> to make it play nice with grub and LVM.
> 
> My question: is it possible to do a new install into a sort of "degraded"
> RAID1 setup with only a single drive, and then add the second drive later,
> or do I need to wait until I acquire the second drive before installing?

It could be done, but I doubt any linux distribution installer supports
it.  So it would involve manual work.

As for device mapper, don't use it.  Really.  Just don't.  It doesn't
work with any of the bootloaders properly, and if a disk fails it becomes
unbootable until you repair it with the windows tool for that particular
fakeraid.

If you are only going to run linux on this raid, then use pure linux
software raid, do not get tempted by the fakeraid the BIOS may offer.
Let mdadm do its thing, and tell grub to install to the MBR of both
drives.  Then it works great.

If you for some reason do want to dual boot linux and windows and you want
raid under both and you are not willing to drop a few hundred dollars
on a hardware raid card from 3ware or areca, then it is theoretically
possible to use the fakeraid, and you can even convince grub to use it
with some proding (it won't figure it out automatically) and use mdadm
to manage it (recent mdadm 3.x support fakeraid in intel and the industry
standard format, whatever it is called).  I have this on one machine
at home, and after giving up on device mapper and going to mdadm to
manage it, at least it now can resync and handle drive failures, and
grub2 almost installs automaticly (device mapper only works with grub
0.97 and only with a very convoluted manual install).  I just have one
step left to explain to the initramfs about how to start the raid that
for some reason it still hasn't got right.  So in other words, it is
still extremely painful.

So md software raid, or hardware raid or a lot of headaches.  Those are
the three choices.  I run md raid on almost every machine I deal with,
except a few machines at work that are servers have hardware raid,
and the one fakeraid machine at home which is now using mdadm.

-- 
Len Sorensen
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