Re: RAID (Re: Problem install)
On Wed, 27 Jan 1999 12:05:55 +0100, wrote:
> David Stern dixit:
> >
> > MD driver is "multiple devices." This is used for functions such as
> > making two partitions perform as one large partition ("RAID 0," etc.).
> > Most people do not use the MD driver, but it is needed at install time.
>
> I recall installing the RAID option when installing Debian2.0, as many other
> options I did not know of at the time (such as linear, and support for
> filesystems I don't need). Then I had just one HDD, but now I have two. I
> wouldn't like the machine to try to activate RAID so, how do I get rid of it
> and also the rest (which I guess they'll be resource consuming)?
RAID 0 utilizes multiple hard drives in tandem to improve performance.
Consider /dev/hda and /dev/hdb each have a maximum 5 MB/s throughput.
When utilizing both /dev/hda and /dev/hdb in tandem, 10 MB/s throughput
can be achieved. However, there are drawbacks (if one drive dies, data
recovery is impossible) and alternatives (partitions may be located to
achieve similar results).
Linear append combines partitions end to end. This is useful if a
single partition of sufficient size is unavailable, or if a hard drive
is very large and dividing it into smaller partitions would reduce
block size and decrease wasted space.
Presumably, RAID 0 on one hard drive would impose a significant
performance penalty, because the hard drive must seek more times and
further, and there would also be a small overhead in cpu cycles to
manage the process. Linear append on one hard drive would NOT increase
seeks, although there would be a small overhead in cpu cycles to manage
the process, so there might be a small performance penalty.
As for removing RAID or Linear Append, presumably you must copy the
data to a regular partition, then update /etc/fstab to reflect the
changes and reboot. Be very careful and backup first.
--
David
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dstern@u.washington.edu
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