Summary: Will 2 channels on HBA be seen by SE3310 as 2 hosts.

From: jason kappy <>
Date: Mon Mar 07 2005 - 15:16:15 EST
I got only two replies for this. I think my posting
was  not clear enough. However thank you very much to
Nathan and Bruce Kirkland. Sorry that I should have
mentioned that I am using my Ultra60 only for initial
configuration of array, later it will be attached to

As in my post earlier the host channels were showing
CurrWidth, narrow instead of Wide scsi. This is
because the system to which it was connected was
turned off. As soon as I turned on the sytem the ARRAY
updated the CurrWidth to Wide.  

Here are the very much appreciated replies I got

> 1)  I think you won't have two paths to each disk,
> it's just that six 
> disks will be on one scsi bus, and the other six on
> the other.  If you 
> add a jbod shelf, then each bus will have 12 disks
> on it.  As far as I 
> can tell the advantage with a single unit is that
> you're only having six 
> disks on a scsi bus instead of 12, reducing
> potential bus contention.
> 2)  The scsi bus that the disks are on is not the
> same scsi buses that 
> connect to HBAs, that's what the LUN mapping stuff
> is for.  You map 
> logical disks to 3310 channels which are what
> connect to the HBA.  You 
> might be able to connect to both ports of your HBA
> for a multipath 
> solution, but that seems a bit odd.  If you really
> need or want to do 
> this, I'd look at using a seperate HBA instead of
> both channels of the 
> same expansion card.  (Does your server have a scsi
> port on the 
> motherboard?)
> 3)  The scsi internals of the 3310 are U-160, so
> that may be why your 
> U-320 HBA is auto-config'ing as narrow.  Not sure
> about this one.
> Best,
> --Nathan

I don't know what a SE3310 is but in general yes 2
paths may give you
some speed. It depends very much on how fast the
arrray is and how much
the i/o bus will take on an Ultra 320. If your dual
port hba runs at 2
gb that is about 200 megabyes for each port in each
direction (fibre
channal is full duplex). So will the 320 push
something like 800 MB/s -
doubtfull. You also need software to deal w/the
mulitple ports - 
DMP, EMC Powerpath ... others. 
In addition to speed the dual porting is usually a
availability feature
- of course that depends, do you have dual switches
and dual 
to your array. 

> jason kappy wrote:
> > Hi Guru's
> >               I have a new SE3310 to be
> configured.  I have two questions
> > 1) I am not sure whether I understand the purpose
> of Dual-bus configuration. According to figures I
> see I guess there would be performance gain because
> of two physical paths to disks.
> >  
> > 2)I have a HBA with two channels on it. Can I
> configure SE3310 in dual-bus with two hosts
> configuration and connect to two different channels
> on a single HBA of one system. Will there be any
> advantages to this? Again I guess two different
> physical paths to array from system. 
> >  
> > Forgive my ignorance if I sound stupid. Also if my
> HBA is Ultra 320 then I need to setup width of Host
> channels  to wide. By default it took narrow as
> shown in below figure. 
> > 
> >

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Received on Mon Mar 7 15:17:17 2005

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