[SunRescue] Damn brainfart on the raid explanation
rescue at sunhelp.org
Sat Dec 2 05:31:55 CST 2000
Sorry, I had a brainfart on my RAID explanation reversing RAID 1 and RAID 0.
RAID 0 is striping, and RAID 1 is mirroring. I didn't even realize I had
done it until I hit the send button.
Doncha hate it when that happens.
Anyway basically reverse all of refernces to 1 and 0 and the explanation is
From: Christopher Byrne [mailto:chris at chrisbyrne.com]
Sent: Saturday, December 02, 2000 03:27
To: 'rescue at sunhelp.org'
Subject: Info on Sun Multipack and disk arrays in general (long)
RAID 0: Mirroring. All data from one drive is simultaneously written to
another drive. 100% redundancy, decrease in write performance, modest
increase in read performance. The problem with this is that you need to
double the number of drives for the same capacity. Mirrors can also be made
hot swappable. This is the most common type of RAID.
RAID 1: Striping. A group of drives is logically combined, and data is
written across all of the drives simultaneously in stripes or "chunks". This
radically improves all performance because the system can read "chunks' of
data from more than one disk at a time (or write). It aslo seriously reduces
reliability because if any single disk in a stripe set fails all of the data
can be lost. This also has the effect of creating a single very large
logical volume to the operating system, which allows you to create
filesystems far larger than a single disk could support. Technically this
isnt really RAID becasue it isnt redundant, but it's a part of the
standards. Also drives in a stripe set are not hot swappable.
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