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solaris sd.conf lun

Posted on 2002-05-17
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Hi,
    I am confuse what is meant by a LUN beside that
it's  alogical number?  Can some please explain in
detail and example?  -thanks-

I have a three lines from sd.conf:
name="sd" parent="lpfc" target=0 lun=1;
name="sd" parent="lpfc" target=0 lun=2;
name="sd" parent="lpfc" target=0 lun=3;


Q2:  does this mean this mean there are 3 LUNs according
    to sd.conf?

LUN1 is c0t0
LUN2 is c2t0
LUN3 is c3t0


thanks in advance
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Question by:siunix
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by:besky
ID: 7018101
No is the answre to question 2.

lun:s are mostly refered to as disknumber in Solaris.

On a scsi system the Solaris naming convention is
c0t0d0s0 for one of its partitions.(Logical name)

c0 is controller 0  ( first conrtoller in system )

t0 is target 0 ( first target on this controller )
targetnumbers are sometimes refered to as SCSI-ID, 0-7
on SCSI-2 and 0-15 on SCSI-3

Target is sometimes an embedded controller in (on) a disk or tape BUT there some "intelligent" targetcontrollers
that can have more that one disk attached.
Disk arrays is an example, take the SSA, this box has six targetnumers internally, 0 - 5 where every target can control six disks 0-5. ( 36 disks in total on 1 controller with 6 targets)
These disks are refered to via the disknumber or as
you might call it Logical Unit Number, lun.

So d0 is disk 0 or LUN 0  ( the first disk on a target )

s0 is the first slice of 8  (or partition)

You can see the lun:s on your system in the message buffer from boot. Just type "dmesg" or check /var/adm/messages*

HTH

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Expert Comment

by:tfewster
ID: 7021607
I'm not a Solaris specialist, so get someone else to confirm this...

A LUN can be a device presented to Solaris by a storage array, e.g. a 20Gb stripe across 3 72Gb disks in a RAID 5 set. As far as Solaris is concerned, it's a 20 Gb disk. The storage array looks after the RAID stuff, partitioning of the RAID set into LUNs and presenting them to the appropriate servers.

You may have alternate hardware paths to the same LUN for failover and load balancing, e.g. if you had multiple SCSI/Fibre Channel interface cards connected to the storage array. AFAIK, sd.conf lists the _controllers_ on the storage array, not all the LUNS on that controller (so you can add more LUNs "dynamically" without having to edit sd.conf)
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Accepted Solution

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besky earned 150 total points
ID: 7021979
Sorry, little too quick there, didnt see the FC driver

But basicly its is the same for fibrechannel devices.
The driver default supports one LUN/target but can be configured to support 256 by adding to sd.conf ( can be diferent with different vendor boards)

And to answer your second question, yes there is one lun/hostadaptor. In your case three.
 There must be at least one lun or the driver will not load

RAID manager and other systempgms also has references to luns as tfewster wrote
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