Re: Software vs. Hardware RAID 1

Walter Mautner <leafnewnode.20.eatallspam@xxxxxxxxxxxxxxx> wrote in
news:80tbo3-1rv.ln1@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx:

x0054 wrote:

I am building a SFF server for my apartment. The case I picked has 2
HD bays which I intend to fill with 2 ATA100 250GB drives. The
motherboard has 2 ATA133/100 IDE buses.

If I go with Software RAID1 I would have HD1 as master on the primary
IDE bus and HD2 as master on secondary IDE bus with the CD drive as
slave on the same bus.

No problem then.

What I am wondering is how would Software RAID1 compare with HW RAID1
and if there are any significant advantages or drawbacks to either?
Also, is it a problem that HD2 will share IDE bus with my CD drive?
(I only really going to use the CD drive to install linux)

Most of the times you are better off with sw raid1: linux can boot
from it, even when one drive goes tits up, but you need to initiate a
resync manually after changing the faulty drive.
A software raid *can* lock up when a hd dies on the job or locks the
ide controller. You may have to physically unplug the ide cable of the
defective drive to be able to reboot.

What's the chance that it would happen? I would be running 2.6 kernel.
One of the most compelling reasons to me, for running SW Raid, was
actually the ability to monitor it from linux and have the system email
me if a disk fails. Sucks if the system locks up.

The advantage of sw raid (mdadm setup with persistent superblocks) is,
you can have multiple partitions with differen raid strategy (raid1
for /, /usr, /home, raid0 for /var and /tmp as an example), and you
can move the disks to another mainboard with a different ide/sata
controller if yours breaks. Which may become difficult with onboard hw
raid. Beware: most onboard "hw raid" is actually "hostraid": the bios
can create and format a raid set, and work with dos - but for windows
you need F6/install driver, similar for linux if available. *And* you
are lost when your old mobo breaks 2 years later without identical
replacement available. Same goes for pci hw raid controllers, though
they are moveable to a new board. These are not dirt cheap though ...


The pci HW Raid boards I had were about $18 shipped for dual ATA133 from
ebay. Worked well with no need for drivers. I see what you mean though.
My new game desktop MB advertised HW Raid capability, but when time came
I needed raid drivers to make windows run on it. So I guess I would be
happier with SW Raid.

Also, in SW RAID1 the kernel makes an image of a drive. Can I then read
each disk independently, just like a normal disk/partition?

Thanks for all the info,

- Bogdan
.

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