Re: HDD vs. RAID (was Re: Lilo Q)
On Mon, Jun 10, 2002 at 10:00:16AM -0400, Ian D. Stewart wrote:
> So, the way I'm reading this, a RAID 5 stack w/ 5 20 GB hard drives
> provides improved access speed and reliability at the cost of slightly
> reduced storage.
Yep. Different RAID levels are basically different tradeoffs between
reliability and capacity (speed should theoretically be improved at all
levels, so I don't see it as a major distinguishing factor, even though
it's not an even increase at all levels in the real world). RAID0 is
all about capacity, RAID1 is the ultimate in failure-tolerance, RAID5 and
RAID0+1 are different ways of trying to strike a balance between the two.
> An earlier thread was making reference to setting up
> seperate controllers for each HDD. I have seen adverts for stand-alone
> RAID towers. Would the use of one of these towers do away with the
> need for seperate controllers, and if so do these towers support IDE or
> just SCSI?
Any sort of true hardware RAID setup (beware the hybrids, since this
doesn't apply to them) will interact with the rest of the system as a
single device. The question of whether to put the individual drives
on separate controllers or not doesn't apply, since the drives
connect to the RAID controller and the RAID controller attaches to
the SCSI (or IDE, I suppose, though I've never seen an IDE hardware
RAID controller) bus as a single device. Even the BIOS thinks it's
just one disk.
Keep in mind, though, that my earlier comment about needing a
seperate controller for each drive is IDE-specific. SCSI controllers
are a lot smarter about handling multiple devices and can deal with
this more effectively, just so long as you verify that the SCSI
controller has enough bandwidth for all the drives to transfer data
at their maximum rates.
--
When we reduce our own liberties to stop terrorism, the terrorists
have already won. - reverius
Innocence is no protection when governments go bad. - Tom Swiss
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