From: Shin (shin@solarider.org)
Date: Sun Mar 21 2004 - 16:30:41 EST
Hi,
I just reliased that I have asked a number of questions, without
truly understanding the point of a LUNs, specifically multiple LUNs
on a device.
I have an A1000, which is setup as Raid5 + 1 hot spare. This has 1
LUN on it. I believe this is the default setup.
When I run format I see this as one big slice (s2). My limited
understanding is that using RaidManager I can setup multiple LUNs on
this device.
Why would I want to do this - does this give me something special
over and above just slicing this s2 into a number of slices to
create filesystems on as opposed to creating multiple LUNs and then
creating slices on each LUN; which I then create file systems on? As
I see it I get the same effect; ie multiple slices both ways but the
1 LUN method needs less effort.
Am I correct in assuming that If I have 1 LUN on 1 A1000 then I see something
like c1t0d0s2 when I run format. With s2 being the total space
available after the Raid 5 and hot spare overhead are take into
account.
But if I created 3 LUNs on the 1 A1000 then I'd see something like
c1t0d0s2, c1t0d1s2, c1t0d2s2 ? Am I losing space with this approach
or is the underlying Raid5 + hot spare acting in exactly the same
way as in the above setup?
If anyone has a link to a good reference to LUNs and their use I'd
appreciate it. Or a link to general use of RAID and what level
should be used when, how to setup LUNs, what software to use to
manage the RAID devices.
I'm trying to learn a lot about RAID very quickly!
Many thanks.
Shin
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