Re: HDD vs. RAID (was Re: Lilo Q)
On Mon, Jun 10, 2002 at 12:07:22PM -0500, Ron Johnson wrote:
> The problem with JBODs (just big ole disks, i.e. single disks)
JBOD = Just a Bunch Of Disks, i.e., several drives operating
independently. A JBOD can be organized into a RAID, but doesn't have
to be.
> With RAID solutions, the read-write heads
> will be in as many different places at once as you have disks.
This is primarily a benefit in RAID0 or 5 configurations. RAID1 could
benefit from it also, but a lot of RAID implementations are too stupid
to take advantage of it. RAID4 loses some of this benefit due to the
limitations of having all the parity data on a single disk.
> Note, though, that since the CPU overhead from calculating RAID[45]
> recovery blocks necessitates a caching controller. Otherwise,
> write speeds will be slower.
RAID1 is also typically slower since the write isn't considered to be
complete until it has taken place on all disks (having read-write heads
in many places helps reads and hurts writes).
--
When we reduce our own liberties to stop terrorism, the terrorists
have already won. - reverius
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